Trigonometry For Beginners!

The Organic Chemistry Tutor
24 Jul 201721:51

Summary

TLDRThis video script offers an in-depth exploration of right triangle trigonometry, focusing on the SOHCAHTOA mnemonic to understand and calculate the sine, cosine, and tangent of an angle in a right triangle. The lesson explains the relationship between the angle, the sides adjacent to and opposite it, and the hypotenuse. It demonstrates how to find missing sides using the Pythagorean theorem and how to calculate the values of the six trigonometric functions (sine, cosine, tangent, cosecant, secant, and cotangent) for given sides of a triangle. The script also covers special right triangles, such as the 3-4-5 triangle, and provides methods to solve for missing angles and sides using trigonometric functions. Additionally, it touches on the application of these concepts in real-world problems and teases an upcoming comprehensive trigonometry course on Udemy, covering topics from angles and the unit circle to trigonometric identities and equations.

Takeaways

  • 📐 **SOHCAHTOA**: A mnemonic for right triangle trigonometry, where Sine is Opposite over Hypotenuse, Cosine is Adjacent over Hypotenuse, and Tangent is Opposite over Adjacent.
  • 🔢 **Pythagorean Theorem**: Applies to right triangles as \( a^2 + b^2 = c^2 \), where \( c \) is the hypotenuse.
  • 🔁 **Reciprocal Functions**: Cosecant is the reciprocal of sine, secant is the reciprocal of cosine, and cotangent is the reciprocal of tangent.
  • 🔍 **Finding Missing Sides**: Use the Pythagorean theorem to find the missing side in a right triangle when two sides are known.
  • 📈 **Special Triangles**: Memorizing special right triangles like 3-4-5, 5-12-13, 8-15-17, and multiples of these can help quickly find missing sides.
  • 📌 **Trigonometric Values**: Calculate the values of sine, cosine, and tangent using the sides of a right triangle relative to an angle.
  • 🔮 **Finding Angles**: Use inverse trigonometric functions (arcsin, arccos, arctan) to find the measure of an angle when the ratio of sides is known.
  • 🔗 **Related Functions**: Tangent relates the opposite and adjacent sides, while cosine and sine relate to the adjacent/hypotenuse and opposite/hypotenuse, respectively.
  • 🧮 **Calculator Usage**: Utilize a calculator in degree mode to find the values of trigonometric functions and their inverses for specific angles.
  • 📚 **Trigonometry Course**: The speaker offers a course on Udemy covering various topics from angles and the unit circle to trigonometric identities and applications.
  • 📈 **Graphing Trigonometric Functions**: Learn how to graph sine, cosine, secant, cosecant, and tangent functions, as well as understand their properties and applications.

Q & A

  • What is the expression 'sohcahtoa' used for in trigonometry?

    -The expression 'sohcahtoa' is a mnemonic for remembering the definitions of the primary trigonometric functions sine, cosine, and tangent in terms of the sides of a right triangle. 'S' stands for sine, 'O' for opposite, 'H' for hypotenuse, 'C' for cosine, 'A' for adjacent, and 'TOA' for tangent.

  • What are the three sides of a right triangle that are relevant to trigonometry?

    -The three sides of a right triangle relevant to trigonometry are the opposite side (to the angle theta), the adjacent side (next to the angle theta), and the hypotenuse (the longest side, across from the right angle).

  • What is the Pythagorean theorem, and how does it apply to right triangles?

    -The Pythagorean theorem states that in a right triangle, the square of the length of the hypotenuse (c) is equal to the sum of the squares of the lengths of the other two sides (a and b). Expressed as an equation, it is a^2 + b^2 = c^2.

  • How do you find the missing side of a right triangle when given the values of two sides?

    -To find the missing side of a right triangle when two sides are given, you use the Pythagorean theorem (a^2 + b^2 = c^2). Substitute the known side lengths for 'a' and 'b', solve for 'c', and then take the square root of the result to find the length of the hypotenuse.

  • What are the reciprocal trigonometric functions, and how are they related to the primary ones?

    -The reciprocal trigonometric functions are cosecant (csc), secant (sec), and cotangent (cot). Cosecant is the reciprocal of sine (csc θ = 1/sin θ), secant is the reciprocal of cosine (sec θ = 1/cos θ), and cotangent is the reciprocal of tangent (cot θ = 1/tan θ).

  • What are some special right triangles with whole number side lengths?

    -Special right triangles with whole number side lengths include the 3-4-5 triangle, the 5-12-13 triangle, the 8-15-17 triangle, and the 7-24-25 triangle. These triangles are derived from the Pythagorean theorem and have side lengths that are multiples of the smallest Pythagorean triple (3, 4, 5).

  • How do you calculate the values of the six trigonometric functions for a given right triangle?

    -To calculate the values of the six trigonometric functions (sine, cosine, tangent, cosecant, secant, and cotangent) for a given right triangle, you first identify the lengths of the opposite, adjacent, and hypotenuse sides relative to the angle in question. Then, apply the definitions of each trigonometric function using these side lengths.

  • How can you find the missing side of a right triangle if you know the angle and one side?

    -If you know one side and an angle in a right triangle, you can find the missing side by using the appropriate trigonometric function related to the known side: sine for the opposite side, cosine for the adjacent side, or tangent for the ratio of the opposite to the adjacent side. Then, apply the Pythagorean theorem to find the hypotenuse if needed.

  • What is the process to find the angle theta in a right triangle if you are given the lengths of the opposite and adjacent sides?

    -To find the angle theta when the lengths of the opposite and adjacent sides are known, use the tangent function, which is the ratio of the opposite side to the adjacent side (tan θ = opposite/adjacent). Then, use the inverse tangent function (arctan or tan^(-1)) to find the angle theta.

  • How do you find the value of an angle in a right triangle if you know the lengths of the hypotenuse and the adjacent side?

    -To find the value of an angle in a right triangle when the lengths of the hypotenuse and the adjacent side are known, use the cosine function (cos θ = adjacent/hypotenuse). Then, apply the inverse cosine function (arccos or cos^(-1)) to determine the angle.

  • What is the purpose of the trigonometry course mentioned in the script?

    -The purpose of the trigonometry course is to provide a comprehensive understanding of trigonometry concepts, including angles, the unit circle, right triangle trigonometry, trigonometric functions, and their applications. The course also covers solving trigonometric equations, verifying trig identities, and using trigonometric functions to solve real-world problems.

Outlines

00:00

📐 Introduction to Right Triangle Trigonometry

This paragraph introduces the concept of right triangle trigonometry, focusing on the SOHCAHTOA mnemonic to remember the relationships between the sides and angles of a right triangle. It explains the terms 'opposite', 'adjacent', and 'hypotenuse' in relation to an angle theta, and how these sides are used in the definitions of the primary trigonometric functions: sine, cosine, and tangent. It also covers the reciprocal functions: cosecant, secant, and cotangent. The Pythagorean theorem is mentioned as a tool to find missing sides. The paragraph concludes with an example of finding the missing side of a triangle with given side lengths and subsequently calculating all six trigonometric functions for that triangle.

05:01

🔢 Applying Trigonometric Functions to Find Missing Sides

This paragraph continues the discussion on right triangle trigonometry by demonstrating how to find missing sides using the Pythagorean theorem and then calculating the values of all six trigonometric functions for a given triangle. It provides a step-by-step example using a triangle with sides of lengths 8 and 17, showing how to determine the missing side and then use SOHCAHTOA to find the values of sine, cosine, tangent, cosecant, secant, and cotangent. The paragraph also mentions special right triangles and their multiples as a quick way to find missing sides without the Pythagorean theorem.

10:02

🧮 Solving Triangles with Given Sides and Calculating Trigonometric Functions

The paragraph presents a method for solving right triangles when the lengths of two sides and one angle are known. It illustrates the process of finding the missing side using the Pythagorean theorem and then applying trigonometric functions to find the values of sine, cosine, and tangent. The reciprocal functions are also calculated by inverting the ratios. The paragraph includes an example with a hypotenuse of 25 and a side of 15, showing that the missing side is 20, and then calculates the trigonometric functions for this specific triangle.

15:03

📐 Using Trigonometric Functions to Find Angles and Sides

This paragraph discusses how to use trigonometric functions to find missing angles and sides in a right triangle. It provides examples of using tangent, cosine, and sine functions to solve for an unknown side when the angle and one side are known. The paragraph demonstrates cross-multiplication and the use of a calculator to find the values of unknown sides for different given angles and side lengths. It emphasizes the importance of setting up the trigonometric equation correctly and using the appropriate function based on the given information.

20:03

📚 Accessing a Comprehensive Trigonometry Course

The final paragraph promotes a comprehensive trigonometry course available on Udemy that covers a wide range of topics in trigonometry. It outlines the course content, which includes angles, radians, the unit circle, right triangle trigonometry, trigonometric functions of any angle, graphs of trigonometric functions, inverse trig functions, composition of trig functions, applications, verifying trig identities, and various trigonometric formulas. The paragraph also mentions that some sections are still being added and provides instructions on how to find and access the course.

🔍 Further Topics and Course Completion

This paragraph mentions additional topics that will be included in the trigonometry course, such as the law of sines, law of cosines, polar coordinates, and others. It notes that about two-thirds of the course has been completed and that more content will be added over time. The paragraph invites students to ask questions and thanks them for watching the video.

Mindmap

Keywords

💡Sohcahtoa

Sohcahtoa is a mnemonic used to remember the definitions of the primary trigonometric functions for acute angles in a right triangle. The acronym stands for 'Sine is Opposite over Hypotenuse, Cosine is Adjacent over Hypotenuse, Tangent is Opposite over Adjacent.' It is central to the video's theme of right triangle trigonometry, helping to relate the angles of a triangle to the lengths of its sides. In the script, it is used to explain how to calculate sine, cosine, and tangent for an angle theta in a right triangle.

💡Right Triangle Trigonometry

Right triangle trigonometry is the study of the relationships between the angles and sides of a right triangle, particularly using the primary trigonometric functions: sine, cosine, and tangent. It is the main theme of the video, which focuses on how to use these relationships to solve for missing side lengths and angles in a right triangle. The script provides several examples of using trigonometric functions to find missing sides and angles in various right triangles.

💡Pythagorean Theorem

The Pythagorean theorem is a fundamental principle in geometry that states in a right triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the lengths of the other two sides. This theorem is used in the script to find the missing side of a right triangle when the lengths of the other two sides are known, as in the example where sides of lengths 3 and 4 are given to find the hypotenuse.

💡Trigonometric Functions

Trigonometric functions, such as sine, cosine, and tangent, are mathematical functions that describe the relationship between the angles and sides of a right triangle. In the video, these functions are used to solve for missing sides and angles in right triangles. The script explains how to calculate these functions using the sides of a triangle and provides examples of their application in solving trigonometry problems.

💡Special Right Triangles

Special right triangles are right triangles with side lengths that have specific integer ratios, such as 3-4-5 or 5-12-13. These triangles are important in the video because they allow for quick identification of missing sides without the need for complex calculations. The script mentions several special triangles and their multiples, which can be used as shortcuts for finding missing sides in similar triangles.

💡Reciprocal Trigonometric Functions

Reciprocal trigonometric functions, such as cosecant, secant, and cotangent, are the reciprocals of the primary trigonometric functions sine, cosine, and tangent, respectively. They are introduced in the script as a means to find the lengths of sides in a right triangle when given the values of the primary trigonometric functions. For instance, the cosecant is the reciprocal of sine, secant is the reciprocal of cosine, and cotangent is the reciprocal of tangent.

💡Inverse Trigonometric Functions

Inverse trigonometric functions, also known as arc functions, are used to find the measure of an angle from the known values of a trigonometric function. In the video, the inverse functions are used to determine angles when the lengths of the sides of a right triangle are known. For example, the script shows how to use the arc tangent function to find an angle when the tangent of that angle is given.

💡Angle of Elevation and Depression

The angle of elevation and depression are concepts used to describe the angle of sight from an observer's line of sight to an object above or below the horizontal line of sight, respectively. While not explicitly detailed in the script, it is implied as a potential application of right triangle trigonometry when discussing the use of trigonometric functions to solve real-world problems.

💡Unit Circle

The unit circle is a circle with a radius of one unit and is used in the context of the video to define the trigonometric functions for all angles, not just those in right triangles. It is a fundamental concept in trigonometry that extends the application of trigonometric functions to include angles greater than 90 degrees. The script mentions the unit circle in relation to the six trigonometric functions and their definitions.

💡Trigonometric Identities

Trigonometric identities are equations that hold true for all values of the variables involved and are used to simplify and manipulate trigonometric expressions. The script briefly mentions verifying trig identities as a challenging aspect of trigonometry, which involves proving that two trigonometric expressions are equivalent using properties and relationships of the trigonometric functions.

💡Trigonometry Course

The script concludes with a reference to a trigonometry course available on the Udemy platform. The course is designed to cover various aspects of trigonometry, including angles, the unit circle, right triangle trigonometry, and applications of trigonometric functions. The mention of the course serves as a resource for viewers who wish to deepen their understanding of the subject matter presented in the video.

Highlights

The expression 'sohcahtoa' is introduced as a mnemonic for the sine, cosine, and tangent ratios in right triangle trigonometry.

The sides of a right triangle are defined as opposite, adjacent, and hypotenuse relative to an angle theta.

The Pythagorean theorem is mentioned in the context of right triangles, stated as a squared plus b squared equals c squared.

Six trigonometric functions are explained using the 'sohcahtoa' mnemonic: sine, cosine, tangent, cosecant, secant, and cotangent.

The process of finding the missing side of a right triangle using the Pythagorean theorem is demonstrated.

Special right triangles with side ratios like 3-4-5 and 5-12-13 are introduced to simplify finding missing sides.

Values of sine, cosine, and tangent for a given right triangle are calculated using the 'sohcahtoa' mnemonic.

The reciprocal trigonometric functions cosecant, secant, and cotangent are derived from their respective primary functions.

An example problem is solved to find the missing side and the values of all six trigonometric functions for a given triangle.

The concept of special triplets for right triangles is used to find missing sides without using the Pythagorean theorem.

The values of the six trigonometric functions are found for a triangle with sides of lengths 8 and 17, using the 'sohcahtoa' mnemonic.

The hypotenuse of a right triangle is calculated when two other sides are known, using the Pythagorean theorem.

Trigonometric function values are calculated for a triangle with a hypotenuse of 25 and a side of 15, illustrating the 'sohcahtoa' mnemonic.

The process of finding the value of an unknown side (x) in a right triangle using tangent is demonstrated with an example.

Calculating the value of x using cosine when the adjacent side and the hypotenuse are known is shown step by step.

An example is provided to find the value of x using sine when the opposite side and the hypotenuse are given.

The method to find the angle theta using tangent when the opposite and adjacent sides are known is explained.

The course curriculum for a comprehensive trigonometry course is outlined, covering topics from angles and the unit circle to trigonometric identities and applications.

Access to the trigonometry course on Udemy is provided for interested learners to deepen their understanding of the subject.

Transcripts

play00:02

have you ever heard of the expression

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sohcahtoa

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what do you think this expression means

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in this lesson we're going to focus on

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right triangle trigonometry

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let's say if this is the angle theta

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now there's three sides of this triangle

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that you need to be familiar with

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opposite to theta this is the opposite

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side

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and next to the angle of theta is the

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adjacent side

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and across the box or the right angle of

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the triangle which is the hypotenuse

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that's the longer side of the triangle

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now if you recall

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this is a b and c the pythagorean

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theorem applies to right triangles a

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squared plus b squared is equal to c

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squared

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but we're not going to focus on that too

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much but just be familiar with that

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equation

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now let's talk about the six trig

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functions in terms of sine cosine

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tangent

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opposite adjacent hypotenuse

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sine theta

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according to sohcahtoa

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s is for sine o is for opposite h is for

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hypotenuse sine theta is equal to the

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opposite side

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divided by the hypotenuse

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cosine theta

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is equal to the adjacent side

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divided by the hypotenuse

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k

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is for cosine is adjacent over

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hypotenuse

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and tangent theta

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toa

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is equal to the opposite side divided by

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the adjacent side so that's the tangent

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ratio it's opposite over adjacent

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now we know that cosecant

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is one over sine so cosecant is

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basically hypotenuse divided by the

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opposite side you just need to flip

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this particular fraction

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secant

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is the reciprocal

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of cosine so secant is going to be

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hypotenuse divided by the adjacent side

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cotangent

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is the reciprocal of tangent so if

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tangent is opposite over adjacent

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cotangent is adjacent divided by the

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opposite side

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now let's say if we're given

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a right triangle

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and we have the value of two sides let's

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say this is three and this is four

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and here is the angle theta

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find the missing side of this right

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triangle

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and then

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find the values of all six trigonometric

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functions sine cosine tangent secant

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cosecant cotangent

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now to find the missing side

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we need to use the pythagorean theorem

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a squared plus b squared is equal to c

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squared

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so a is three b is four

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and we gotta find missing side

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c

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which is the hypotenuse

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three squared is nine four squared is

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sixteen

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nine plus sixteen is 25

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and if you take the square root of both

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sides

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you can see that the hypotenuse is 5.

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now it turns out that there are some

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special numbers

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there's the three four five right

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triangle the 5 12 13 right triangle

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the 8 15 17 right triangle

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and the 7 24 25 right triangle

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and any whole number ratios or multiples

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of these numbers will also work for

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example if we multiply this by 2

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we'll get 6 8 10.

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that can also work or

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if you multiply by 3

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you get the 9 12 15 triangle

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if you multiply this one by 2 you get

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the 10

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24 26 triangle

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those are also special triplets

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they work with any right triangle

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now some other numbers that

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are less common but you might see

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are the 9 40 41 triangle and the 1160

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61.

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so if you see some of these numbers you

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can find the missing side quickly

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if you know them

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so now let's finish this problem

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so what is the value of sine theta

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so according to sohcahtoa

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we know that sine theta

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is equal to the opposite side divided by

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the adjacent side

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and the part so

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soh

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opposite to

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theta

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is

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4.

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and hypotenuse is five so therefore sine

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theta

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is going to be four divided by five

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now cosine theta

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is equal to the adjacent side divided by

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the hypotenuse

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we said 4 is the opposite side

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5 is the hypotenuse and 3 is the

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adjacent side so in this case is going

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to be 3 divided by 5.

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so that's the value of cosine

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now let's find the value of tangent

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tangent theta according to toa

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is equal to the opposite side divided by

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the adjacent side

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so that's going to be 4 divided by 3

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so that's the value of tangent

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now once we have these three we can

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easily find the other three

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to find cosecant

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it's one over sine so just flip this

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fraction is going to be five over four

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and secant is the reciprocal of cosine

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so flip this fraction secant is going to

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be five over three

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cotangent is the reciprocal of tangent

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so if cotan i mean if tangent's four

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over three cotangent is going to be

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three over four and that's how you could

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find the value of the six trigonometric

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functions

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let's try another problem

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so let's say this is theta again

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and this side is eight and this side is

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17.

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find the missing side

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and then

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use the completed triangle to find the

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value of the six trigonometric functions

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so go ahead and pause the video and work

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on this problem

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so first we need to know that this is

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the 8 15 17 triangle

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if you ever forget you can fall back to

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this equation

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so a is 8 we're looking for the missing

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side b and the hypotenuse is 17.

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8 squared is 64

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and 17 squared is 289

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289 minus 64 is 225

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and we need to take the square root of

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both sides and the square root of 225 is

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15

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which gives us the missing side of the

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triangle

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so now go ahead and find the value of

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sine theta

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cosine theta

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tangent theta

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and then cosecant theta

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secant theta

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and cotangent theta

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so using sohcahtoa

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we know that sine

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is equal to the opposite side divided by

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the hypotenuse

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so let's label all the three sides 17 is

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the hypotenuse

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8 is the adjacent side

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and opposite to theta is 15.

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so opposite over hypotenuse this is

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going to be 15 divided by 17.

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so that is the value

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of sine theta now cosine theta

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is going to be equal to the adjacent

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side

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divided by the hypotenuse

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so the adjacent side is 8 they have hot

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news is 17. so cosine theta

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is 8 over 17.

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tangent based on toa is going to be

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opposite

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over adjacent

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so opposite is 15 adjacent is 8.

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therefore tangent

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is going to be 15 divided by eight

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now cosecant is the reciprocal of sine

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so if sine theta is 15 over 17 cosecant

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is going to be 17 over 15.

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secant is the reciprocal of cosine so if

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cosine is 8 over 17 secant is 17 over 8.

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you just got to flip it and cotan is a

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reciprocal of tangent

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so cotangent is going to be 8 over 15.

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just flip this fraction

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and now we have the values

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of the six trigonometric functions

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and that's all you gotta do

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so here's a different problem

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so let's say here's our right angle and

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this time this is theta

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and let's say the hypotenuse is 25

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and this side is 15.

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find the missing side and then go ahead

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and find the value of the six

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trigonometric functions

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so this is going to be similar to the

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three four five triangle

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notice that if we multiply everything by

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five

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we'll get two

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of the three numbers that we need three

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times five is fifteen four times five is

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twenty five times five is twenty five

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so we have the fifteen

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and we have the twenty five

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therefore the missing side must be

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twenty

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and you could use the pythagorean

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theorem to confirm this if you want to

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so now let's go ahead and find the value

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of sine theta

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so opposite to theta

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is 20.

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the hypotenuse is always across the box

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it's the longer side

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so 27 is the hypotenuse

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and adjacent to 15 or right next to it

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is 15.

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i mean adjacent to theta is 15.

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now sine theta we know it's opposite

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divided by hypotenuse so it's 20

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over 25

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which reduces to 4 over 5.

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if we divide both numbers by 5. 20

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divided by 5 is 4

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25 divided by 5 is 5.

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cosine theta

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is adjacent over hypotenuse so that's 15

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divided by 25 which reduces to 3 divided

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by 5.

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tangent theta

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is opposite over adjacent

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so 20 over 15

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which

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becomes

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if you divide by 5 that's going to be 4

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over 3.

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now cosecant is the reciprocal of sine

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so it's going to be 5 over 4

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based on

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this value

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and if cosine is 3 over 5

play10:47

then secant the reciprocal of cosine has

play10:49

to be 5 divided by 3.

play10:52

now if tangent

play10:54

is 4 over 3 cotangent has to be 3

play10:58

divided by 4.

play11:00

and so that's it for this problem

play11:04

consider the right triangle

play11:08

in this right triangle find

play11:10

the missing side in this case find the

play11:12

value of x let's say the angle is 38

play11:15

degrees

play11:16

and this side is 42.

play11:19

so what trig function

play11:21

should you use in order to find the

play11:23

value of x

play11:24

should we use sine cosine or tangent

play11:27

well relative to 38

play11:30

we have the opposite side

play11:32

which is x

play11:34

and the adjacent side

play11:36

which is 42.

play11:37

so tangent we know it's opposite over

play11:39

adjacent so therefore tangent

play11:42

of the angle 38 degrees

play11:44

is equal to the opposite side x

play11:47

divided by the adjacent side 42

play11:50

so in order to get x by itself we need

play11:51

to multiply both sides by 42.

play11:56

so these will cancel

play11:57

so therefore x

play11:59

is equal to 42

play12:01

tangent of 38

play12:04

so we need to use the calculator to get

play12:06

this answer

play12:07

and make sure your calculator is in

play12:09

degree mode

play12:12

so tan 38

play12:14

which is 0.7813

play12:19

and let's multiply that by 42

play12:22

so this will give you an x value of 32.8

play12:31

now let's try another example

play12:37

feel free to pause the video to work on

play12:38

each of these problems by the way

play12:41

so let's say this angle is 54 degrees

play12:44

and we're looking for the value of x and

play12:47

hypotenuse is 26

play12:49

which trig function should we use sine

play12:52

cosine of tangent

play12:54

so opposite to the right angle we know

play12:56

it's the hypotenuse

play12:58

and x is on the adjacent side relative

play13:01

to 54.

play13:03

so cosine

play13:04

is associated with adjacent and

play13:06

hypotenuse

play13:07

so therefore cosine of the angle 54

play13:10

is equal to the adjacent side x divided

play13:13

by

play13:13

the hypotenuse of 26

play13:16

so to get x by itself we got to multiply

play13:18

both sides by 26

play13:22

so therefore x

play13:23

is equal to 26

play13:26

cosine

play13:27

of 54 degrees

play13:31

cosine 54

play13:32

is 0.587785

play13:36

if we multiply that by 26

play13:38

this will give us the value of x which

play13:40

is 15.28

play13:48

here's another one that we could try

play13:53

let's say the angle is 32 degrees

play13:56

and the hypotenuse is x

play13:58

and this is 12.

play14:00

so notice that 12 is opposite to

play14:04

32

play14:06

and we have the hypotenuse so this time

play14:08

we need to use the sine function

play14:12

sine of the angle 32

play14:14

is equal to the opposite side 12

play14:16

divided by x

play14:20

so in this case what can we do to find

play14:22

the value of x

play14:27

what would you do

play14:30

what i would do is cross multiply

play14:32

so 1 times 12

play14:35

is 12

play14:36

and this is going to equal

play14:39

x times sine 32.

play14:44

next

play14:45

i recommend dividing both sides by sine

play14:47

thirty-two

play14:51

sine thirty-two divided by itself is one

play14:54

so therefore x

play14:56

is equal to 12

play14:58

over sine 32.

play15:02

12 divided by sine 32 is 22.64

play15:08

so that's the value of x in this

play15:10

particular problem

play15:12

now let's work on another problem

play15:15

so this time

play15:17

we need to find the angle theta

play15:20

and we're given these two sides

play15:24

so 5 is opposite to the angle

play15:28

and 4 is adjacent to it

play15:31

so what trig function

play15:33

can relate theta 4 and 5

play15:36

we know tangent is opposite over

play15:38

adjacent so tangent of the angle theta

play15:41

is equal to the opposite side which is 5

play15:44

divided by the adjacent side 4.

play15:47

so how can we find the value of the

play15:48

angle theta

play15:50

if tangent theta is 5 over 4

play15:53

and then theta

play15:54

is going to be the inverse tangent or

play15:57

arc tangent of 5 over 4 and you simply

play16:00

have to type this in your calculator

play16:02

so type in

play16:04

arc tan 5 over 4

play16:07

and you should get an angle

play16:09

of

play16:10

51.34 degrees

play16:13

so that's how you could find the missing

play16:14

angle

play16:15

let's try another example

play16:22

feel free to pause the video and find a

play16:23

missing angle

play16:25

so in this case we have the adjacent

play16:27

side

play16:28

and we have the hypotenuse

play16:31

so therefore this is associative of

play16:33

cosine

play16:34

cosine theta is equal to the adjacent

play16:36

side

play16:37

divided by the hypotenuse so if cosine

play16:39

theta is equal to 3 divided by 7

play16:42

theta is going to be arc cosine 3 over

play16:45

7.

play16:48

and once again you have to use a

play16:49

calculator to figure this out because

play16:51

without a calculator out of you know

play16:52

what this answer is

play16:54

and this is going to be

play16:56

64.62 degrees

play17:05

so here's another one for you

play17:08

let's say this is 5 and this is 6.

play17:12

go ahead and find the value of theta

play17:14

so the hypotenuse is 6

play17:16

opposites of theta is five

play17:19

so we know sine is associated with

play17:20

opposite and hypotenuse

play17:22

sine theta is equal to the opposite side

play17:24

which is five

play17:25

divided by the hypotenuse which is six

play17:27

therefore theta

play17:29

is the arc sine or inverse sine of five

play17:32

over six

play17:38

and so the angle is going to be

play17:40

56.44 degrees

play17:43

and that's it that's all you got to do

play17:44

to find the missing angle of a right

play17:46

triangle

play17:48

for those of you who might be interested

play17:50

in my trigonometry course

play17:52

here's how you can access it

play17:54

so

play17:55

go to udemy.com

play18:00

and once you're there

play18:04

enter into the search box trigonometry

play18:10

now this is a course i've recently

play18:11

created so

play18:13

i haven't finished

play18:14

adding all the sections that i want to

play18:16

add so anytime i'm going to do that

play18:20

right now the page is accessible on the

play18:22

uh you can find the course on the second

play18:24

page and here it is trigonometry the

play18:26

unit circle angles

play18:28

and right triangles is basically the one

play18:30

with the dark background

play18:31

and a circle with a triangle inside the

play18:34

circle

play18:40

so let's look at the curriculum in the

play18:42

first section

play18:44

i'm going to go over angles

play18:47

radians how to convert degrees to

play18:49

radians

play18:50

coterminal angles

play18:52

how to convert dms to decimal degrees

play18:55

arc length

play18:56

area of the sector of a circle

play18:58

linear speed and angular speed word

play19:00

problems and also if you need to take

play19:03

the time that's shown on the clock and

play19:05

if you need to convert it to an angle

play19:07

measure

play19:08

i cover that in this section as well

play19:10

and then at the end of each section is

play19:11

the video quiz

play19:13

the next section is about the unit

play19:15

circle the six trig functions

play19:17

sine cosine tangent secant cosecant

play19:20

cotan

play19:22

and also reference angles as well

play19:24

after that you have right triangle

play19:26

trigonometry

play19:28

things like sohcahtoa

play19:30

the special right triangles like the

play19:31

30-60-90 triangle

play19:33

you need to know that so you can

play19:35

evaluate

play19:36

sine and cosine

play19:37

functions

play19:38

without using the unit circle

play19:41

next

play19:42

i'm going to talk about how to solve

play19:44

angle of elevation and depression

play19:46

problems

play19:48

and just solving the missing sides of

play19:50

right triangles

play19:52

after that trigonometric functions of

play19:54

any angle

play19:56

and then the graph intrigue functions

play19:58

you need to know how to graph the sine

play19:59

and cosine

play20:00

functions secant cosecant

play20:03

and tangent as well

play20:08

after that

play20:09

inverse trig functions you need to know

play20:11

how to evaluate it

play20:13

and also how to graph it too

play20:15

in addition you need to know how to

play20:16

graph or evaluate composition of trig

play20:19

functions for example we might have

play20:21

sine of inverse cosine of 3 over 4 or

play20:24

something like that and you can use a

play20:26

right triangle

play20:27

to solve those types of problems you'll

play20:29

see when you

play20:31

access that section after that

play20:33

applications of trig functions

play20:35

solving problems to have two right

play20:37

triangles in it

play20:39

and

play20:40

barons as well

play20:42

one of the hardest actions in trig is

play20:44

this section verifying trig identities

play20:47

so that's uh

play20:49

that's a hard one so make sure you spend

play20:50

some time

play20:51

learning that section after that summer

play20:53

difference formulas

play20:56

double angle half angle power reducing

play20:58

formulas

play21:01

product to sum sum to product

play21:03

and also solve and trig equations

play21:05

but there are still some sections i'm

play21:07

going to add to this course like for

play21:09

example law of sines law of cosines

play21:13

polar coordinates and some other topics

play21:15

as well

play21:16

so about two-thirds of the course is

play21:19

finished so far and for most students

play21:21

this is just what they need intrigued

play21:23

but in time you'll see more

play21:25

so now you know how to access the course

play21:26

and if you have any questions let me

play21:28

know

play21:28

so thanks for watching

play21:51

you

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TrigonometrySOHCAHTOAPythagorean TheoremRight TriangleTrig FunctionsSineCosineTangentInverse TrigonometryMath EducationGeometryProblem Solving
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