CONSTRUIR E MEDIR ÂNGULOS UTILIZANDO O TRANSFERIDOR | MATEMÁTICA BÁSICA | \Prof. Gis/

Summary

In this engaging video, the presenter introduces viewers to the concepts of constructing and measuring angles using a protractor. The lesson begins with a historical note about navigators using angles and the sextant to chart their positions. Viewers are then guided through the process of constructing angles of different types: acute, obtuse, and right, while learning the essential parts of a protractor. The video also covers practical techniques for measuring angles accurately, emphasizing alignment and precision. The presenter wraps up with a reminder of how angles have been used for centuries, leaving the audience with useful tips for their studies.

Takeaways

• 😀 The video introduces the concept of constructing and measuring angles using a protractor.
• 😀 Navigators in the past used angles to calculate their position on nautical maps with a tool called a sextant, which had a scale of 70 degrees, a sixth of a full circle.
• 😀 There are two types of protractors: a 360-degree protractor (full circle) and a 180-degree protractor (half circle).
• 😀 Key components of a protractor include the center, the fiducial line (line of faith), and the degree markings (usually in increments of 1 degree).
• 😀 When constructing an angle, it is important to align the protractor’s center with the vertex of the angle and its fiducial line with one of the rays of the angle.
• 😀 For constructing a 68-degree angle, the procedure involves marking the degrees on the protractor, aligning the center and fiducial line, and drawing the second ray of the angle.
• 😀 An obtuse angle, such as a 115-degree angle, is constructed similarly, but the second ray is placed beyond the 90-degree mark, indicating that the angle is greater than 90 degrees.
• 😀 A right angle is a 90-degree angle, and it is constructed by aligning the protractor’s center with the vertex, marking 90 degrees, and drawing the second ray.
• 😀 The video also covers how to measure angles, either by using a 180-degree or 360-degree protractor, depending on the size of the angle being measured.
• 😀 In measuring angles, aligning the protractor’s center with the vertex and the fiducial line with one ray of the angle is essential. The angle is then determined by reading the degree marking.

Q & A

What historical context was provided for the use of angles in navigation?

The video mentions that sailors used angles to calculate their position on nautical maps, employing an instrument called a sextant. The sextant had a scale of 70 degrees, representing one-sixth of a complete circle.

What are the two types of protractors mentioned in the video?

The video mentions two types of protractors: the 360-degree protractor, which has a full circle scale, and the 180-degree protractor, which represents half a circle.

What are the three important parts of a protractor discussed in the script?

The three key parts of a protractor are: the center point (which is aligned with the vertex of the angle), the line of sight (called the 'line of faith'), and the scale, which shows the degree markings from 0 to 180 or 360 degrees depending on the protractor.

How do you construct a 68-degree angle using a protractor?

To construct a 68-degree angle, you first draw a semi-line. Then, you align the center of the protractor with the vertex, ensuring the 'line of faith' aligns with the semi-line. After that, you locate 68 degrees on the protractor scale and mark the angle, drawing the second line from the vertex to complete the angle.

What is the difference between an acute angle and an obtuse angle as demonstrated in the video?

An acute angle is less than 90 degrees, while an obtuse angle is greater than 90 degrees but less than 180 degrees. In the video, a 68-degree angle was classified as acute, and a 115-degree angle was classified as obtuse.

What steps are involved in constructing a 115-degree obtuse angle?

To construct a 115-degree angle, you draw a semi-line, align the protractor's center with the vertex, and adjust the 'line of faith' with the semi-line. Then, you find 115 degrees on the scale (which lies between 110 and 120 degrees), mark the point, and connect the vertex to the point to form the obtuse angle.

How is a right angle (90 degrees) constructed?

A right angle is constructed by drawing a semi-line and aligning the center of the protractor with the vertex. Then, you align the 'line of faith' to the 0-degree mark and draw the second line at the 90-degree point to complete the angle.

What is the procedure for measuring an angle using a protractor?

To measure an angle, you place the center of the protractor on the vertex of the angle and align the 'line of faith' with one side of the angle. Then, you read the degree markings where the other side of the angle intersects the scale of the protractor.

How do you measure an angle greater than 180 degrees?

To measure an angle greater than 180 degrees, you use a 360-degree protractor. Align the center of the protractor with the vertex and the 'line of faith' with one side of the angle. You then count the degrees on the scale in the outer section of the protractor.

What are some methods to improve accuracy when measuring angles with a protractor?

To improve accuracy, you can extend the lines of the angle lightly using a pencil, making it easier to see where they intersect with the scale. This helps ensure precise measurement, especially when the lines are hard to follow.