Name: Construction of Angles Using Protractor
Uploaded: 2019-07-19
Duration: 4 min 7 s
Description: We know that an angle is formed when two rays join at a common point. In this video session, learn how to construct angles using a basic geometry tool called a protractor.

Question

Measure and write all angles of the figure below.

Accepted Answer

Given figure is a triangle. Let us name the triangle as $△ A B C$ .

We are asked to measure and write all the angles of the given triangle.

We can see that there are three angles in the triangle namely $∠ C A B, ∠ A B C & ∠ B C A$ or in short $∠ A, ∠ B & ∠ C$ .

We know that the instrument used to measure an angle is a protractor.

Let us place the protractor over each angle of the triangle to get its measure.

To measure the angle $∠ C$ , place the midpoint of the protractor on the vertex $C$ of $△ A B C$ and align the line segment $C B$ on the zero line of the protractor as shown below.

Since point $B$ is on the $0$ mark on the right side of the protractor, use the inner measurements of the protractor to find the measure of the angle.

The numbers on the protractor are the degree measure of the angles made by these lines with the bottom line marked $0$ .

From, the protractor we can see that the line segment $C A$ is lying on $60 °$ .

Hence, the measure of $∠ C$ is $60 °$ .

Now, rotate the protractor and place the midpoint of the protractor at the vertex $A$ .

Since point $C$ is on the $0$ mark on the right side of the protractor, use the inner measurements of the protractor to find the measure of the angle.

We can see that the line segment $A B$ is lying on $60 °$ .

Hence, the measure of $∠ A$ is $60 °$ .

Now, place the midpoint of the protractor at vertex $B$ .

Since point $C$ is on the $0$ mark on the left side of the protractor, use the outer measurements of the protractor to find the measure of the angle.

We can see that the line segment $A B$ is lying on $60 °$ .

Hence, the measure of $∠ B$ is $60 °$ .

We know that the angles measuring less than $90 °$ are called acute angles.

Hence, all the angles of the triangle $△ A B C$ measuring $60 °$ are acute angles.

Since all the angles are equal and equal to $60 °$ , $△ A B C$ is an equilateral triangle.

Measure and write all angles of the figure below.

Important Questions on Angles

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