Trigonometry For Beginners!
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
📐 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.
🔢 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.
🧮 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.
📐 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.
📚 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
💡Right Triangle Trigonometry
💡Pythagorean Theorem
💡Trigonometric Functions
💡Special Right Triangles
💡Reciprocal Trigonometric Functions
💡Inverse Trigonometric Functions
💡Angle of Elevation and Depression
💡Unit Circle
💡Trigonometric Identities
💡Trigonometry Course
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
have you ever heard of the expression
sohcahtoa
what do you think this expression means
in this lesson we're going to focus on
right triangle trigonometry
let's say if this is the angle theta
now there's three sides of this triangle
that you need to be familiar with
opposite to theta this is the opposite
side
and next to the angle of theta is the
adjacent side
and across the box or the right angle of
the triangle which is the hypotenuse
that's the longer side of the triangle
now if you recall
this is a b and c the pythagorean
theorem applies to right triangles a
squared plus b squared is equal to c
squared
but we're not going to focus on that too
much but just be familiar with that
equation
now let's talk about the six trig
functions in terms of sine cosine
tangent
opposite adjacent hypotenuse
sine theta
according to sohcahtoa
s is for sine o is for opposite h is for
hypotenuse sine theta is equal to the
opposite side
divided by the hypotenuse
cosine theta
is equal to the adjacent side
divided by the hypotenuse
k
is for cosine is adjacent over
hypotenuse
and tangent theta
toa
is equal to the opposite side divided by
the adjacent side so that's the tangent
ratio it's opposite over adjacent
now we know that cosecant
is one over sine so cosecant is
basically hypotenuse divided by the
opposite side you just need to flip
this particular fraction
secant
is the reciprocal
of cosine so secant is going to be
hypotenuse divided by the adjacent side
cotangent
is the reciprocal of tangent so if
tangent is opposite over adjacent
cotangent is adjacent divided by the
opposite side
now let's say if we're given
a right triangle
and we have the value of two sides let's
say this is three and this is four
and here is the angle theta
find the missing side of this right
triangle
and then
find the values of all six trigonometric
functions sine cosine tangent secant
cosecant cotangent
now to find the missing side
we need to use the pythagorean theorem
a squared plus b squared is equal to c
squared
so a is three b is four
and we gotta find missing side
c
which is the hypotenuse
three squared is nine four squared is
sixteen
nine plus sixteen is 25
and if you take the square root of both
sides
you can see that the hypotenuse is 5.
now it turns out that there are some
special numbers
there's the three four five right
triangle the 5 12 13 right triangle
the 8 15 17 right triangle
and the 7 24 25 right triangle
and any whole number ratios or multiples
of these numbers will also work for
example if we multiply this by 2
we'll get 6 8 10.
that can also work or
if you multiply by 3
you get the 9 12 15 triangle
if you multiply this one by 2 you get
the 10
24 26 triangle
those are also special triplets
they work with any right triangle
now some other numbers that
are less common but you might see
are the 9 40 41 triangle and the 1160
61.
so if you see some of these numbers you
can find the missing side quickly
if you know them
so now let's finish this problem
so what is the value of sine theta
so according to sohcahtoa
we know that sine theta
is equal to the opposite side divided by
the adjacent side
and the part so
soh
opposite to
theta
is
4.
and hypotenuse is five so therefore sine
theta
is going to be four divided by five
now cosine theta
is equal to the adjacent side divided by
the hypotenuse
we said 4 is the opposite side
5 is the hypotenuse and 3 is the
adjacent side so in this case is going
to be 3 divided by 5.
so that's the value of cosine
now let's find the value of tangent
tangent theta according to toa
is equal to the opposite side divided by
the adjacent side
so that's going to be 4 divided by 3
so that's the value of tangent
now once we have these three we can
easily find the other three
to find cosecant
it's one over sine so just flip this
fraction is going to be five over four
and secant is the reciprocal of cosine
so flip this fraction secant is going to
be five over three
cotangent is the reciprocal of tangent
so if cotan i mean if tangent's four
over three cotangent is going to be
three over four and that's how you could
find the value of the six trigonometric
functions
let's try another problem
so let's say this is theta again
and this side is eight and this side is
17.
find the missing side
and then
use the completed triangle to find the
value of the six trigonometric functions
so go ahead and pause the video and work
on this problem
so first we need to know that this is
the 8 15 17 triangle
if you ever forget you can fall back to
this equation
so a is 8 we're looking for the missing
side b and the hypotenuse is 17.
8 squared is 64
and 17 squared is 289
289 minus 64 is 225
and we need to take the square root of
both sides and the square root of 225 is
15
which gives us the missing side of the
triangle
so now go ahead and find the value of
sine theta
cosine theta
tangent theta
and then cosecant theta
secant theta
and cotangent theta
so using sohcahtoa
we know that sine
is equal to the opposite side divided by
the hypotenuse
so let's label all the three sides 17 is
the hypotenuse
8 is the adjacent side
and opposite to theta is 15.
so opposite over hypotenuse this is
going to be 15 divided by 17.
so that is the value
of sine theta now cosine theta
is going to be equal to the adjacent
side
divided by the hypotenuse
so the adjacent side is 8 they have hot
news is 17. so cosine theta
is 8 over 17.
tangent based on toa is going to be
opposite
over adjacent
so opposite is 15 adjacent is 8.
therefore tangent
is going to be 15 divided by eight
now cosecant is the reciprocal of sine
so if sine theta is 15 over 17 cosecant
is going to be 17 over 15.
secant is the reciprocal of cosine so if
cosine is 8 over 17 secant is 17 over 8.
you just got to flip it and cotan is a
reciprocal of tangent
so cotangent is going to be 8 over 15.
just flip this fraction
and now we have the values
of the six trigonometric functions
and that's all you gotta do
so here's a different problem
so let's say here's our right angle and
this time this is theta
and let's say the hypotenuse is 25
and this side is 15.
find the missing side and then go ahead
and find the value of the six
trigonometric functions
so this is going to be similar to the
three four five triangle
notice that if we multiply everything by
five
we'll get two
of the three numbers that we need three
times five is fifteen four times five is
twenty five times five is twenty five
so we have the fifteen
and we have the twenty five
therefore the missing side must be
twenty
and you could use the pythagorean
theorem to confirm this if you want to
so now let's go ahead and find the value
of sine theta
so opposite to theta
is 20.
the hypotenuse is always across the box
it's the longer side
so 27 is the hypotenuse
and adjacent to 15 or right next to it
is 15.
i mean adjacent to theta is 15.
now sine theta we know it's opposite
divided by hypotenuse so it's 20
over 25
which reduces to 4 over 5.
if we divide both numbers by 5. 20
divided by 5 is 4
25 divided by 5 is 5.
cosine theta
is adjacent over hypotenuse so that's 15
divided by 25 which reduces to 3 divided
by 5.
tangent theta
is opposite over adjacent
so 20 over 15
which
becomes
if you divide by 5 that's going to be 4
over 3.
now cosecant is the reciprocal of sine
so it's going to be 5 over 4
based on
this value
and if cosine is 3 over 5
then secant the reciprocal of cosine has
to be 5 divided by 3.
now if tangent
is 4 over 3 cotangent has to be 3
divided by 4.
and so that's it for this problem
consider the right triangle
in this right triangle find
the missing side in this case find the
value of x let's say the angle is 38
degrees
and this side is 42.
so what trig function
should you use in order to find the
value of x
should we use sine cosine or tangent
well relative to 38
we have the opposite side
which is x
and the adjacent side
which is 42.
so tangent we know it's opposite over
adjacent so therefore tangent
of the angle 38 degrees
is equal to the opposite side x
divided by the adjacent side 42
so in order to get x by itself we need
to multiply both sides by 42.
so these will cancel
so therefore x
is equal to 42
tangent of 38
so we need to use the calculator to get
this answer
and make sure your calculator is in
degree mode
so tan 38
which is 0.7813
and let's multiply that by 42
so this will give you an x value of 32.8
now let's try another example
feel free to pause the video to work on
each of these problems by the way
so let's say this angle is 54 degrees
and we're looking for the value of x and
hypotenuse is 26
which trig function should we use sine
cosine of tangent
so opposite to the right angle we know
it's the hypotenuse
and x is on the adjacent side relative
to 54.
so cosine
is associated with adjacent and
hypotenuse
so therefore cosine of the angle 54
is equal to the adjacent side x divided
by
the hypotenuse of 26
so to get x by itself we got to multiply
both sides by 26
so therefore x
is equal to 26
cosine
of 54 degrees
cosine 54
is 0.587785
if we multiply that by 26
this will give us the value of x which
is 15.28
here's another one that we could try
let's say the angle is 32 degrees
and the hypotenuse is x
and this is 12.
so notice that 12 is opposite to
32
and we have the hypotenuse so this time
we need to use the sine function
sine of the angle 32
is equal to the opposite side 12
divided by x
so in this case what can we do to find
the value of x
what would you do
what i would do is cross multiply
so 1 times 12
is 12
and this is going to equal
x times sine 32.
next
i recommend dividing both sides by sine
thirty-two
sine thirty-two divided by itself is one
so therefore x
is equal to 12
over sine 32.
12 divided by sine 32 is 22.64
so that's the value of x in this
particular problem
now let's work on another problem
so this time
we need to find the angle theta
and we're given these two sides
so 5 is opposite to the angle
and 4 is adjacent to it
so what trig function
can relate theta 4 and 5
we know tangent is opposite over
adjacent so tangent of the angle theta
is equal to the opposite side which is 5
divided by the adjacent side 4.
so how can we find the value of the
angle theta
if tangent theta is 5 over 4
and then theta
is going to be the inverse tangent or
arc tangent of 5 over 4 and you simply
have to type this in your calculator
so type in
arc tan 5 over 4
and you should get an angle
of
51.34 degrees
so that's how you could find the missing
angle
let's try another example
feel free to pause the video and find a
missing angle
so in this case we have the adjacent
side
and we have the hypotenuse
so therefore this is associative of
cosine
cosine theta is equal to the adjacent
side
divided by the hypotenuse so if cosine
theta is equal to 3 divided by 7
theta is going to be arc cosine 3 over
7.
and once again you have to use a
calculator to figure this out because
without a calculator out of you know
what this answer is
and this is going to be
64.62 degrees
so here's another one for you
let's say this is 5 and this is 6.
go ahead and find the value of theta
so the hypotenuse is 6
opposites of theta is five
so we know sine is associated with
opposite and hypotenuse
sine theta is equal to the opposite side
which is five
divided by the hypotenuse which is six
therefore theta
is the arc sine or inverse sine of five
over six
and so the angle is going to be
56.44 degrees
and that's it that's all you got to do
to find the missing angle of a right
triangle
for those of you who might be interested
in my trigonometry course
here's how you can access it
so
go to udemy.com
and once you're there
enter into the search box trigonometry
now this is a course i've recently
created so
i haven't finished
adding all the sections that i want to
add so anytime i'm going to do that
right now the page is accessible on the
uh you can find the course on the second
page and here it is trigonometry the
unit circle angles
and right triangles is basically the one
with the dark background
and a circle with a triangle inside the
circle
so let's look at the curriculum in the
first section
i'm going to go over angles
radians how to convert degrees to
radians
coterminal angles
how to convert dms to decimal degrees
arc length
area of the sector of a circle
linear speed and angular speed word
problems and also if you need to take
the time that's shown on the clock and
if you need to convert it to an angle
measure
i cover that in this section as well
and then at the end of each section is
the video quiz
the next section is about the unit
circle the six trig functions
sine cosine tangent secant cosecant
cotan
and also reference angles as well
after that you have right triangle
trigonometry
things like sohcahtoa
the special right triangles like the
30-60-90 triangle
you need to know that so you can
evaluate
sine and cosine
functions
without using the unit circle
next
i'm going to talk about how to solve
angle of elevation and depression
problems
and just solving the missing sides of
right triangles
after that trigonometric functions of
any angle
and then the graph intrigue functions
you need to know how to graph the sine
and cosine
functions secant cosecant
and tangent as well
after that
inverse trig functions you need to know
how to evaluate it
and also how to graph it too
in addition you need to know how to
graph or evaluate composition of trig
functions for example we might have
sine of inverse cosine of 3 over 4 or
something like that and you can use a
right triangle
to solve those types of problems you'll
see when you
access that section after that
applications of trig functions
solving problems to have two right
triangles in it
and
barons as well
one of the hardest actions in trig is
this section verifying trig identities
so that's uh
that's a hard one so make sure you spend
some time
learning that section after that summer
difference formulas
double angle half angle power reducing
formulas
product to sum sum to product
and also solve and trig equations
but there are still some sections i'm
going to add to this course like for
example law of sines law of cosines
polar coordinates and some other topics
as well
so about two-thirds of the course is
finished so far and for most students
this is just what they need intrigued
but in time you'll see more
so now you know how to access the course
and if you have any questions let me
know
so thanks for watching
you
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