# How to use a Protractor to measure angles

You can find any given angle using a device named Protractor.
It is easily available in the stationary so make sure to buy one.

Here are some protractors available in the market
All tells the same thing, there is just difference in the designs

Design 01

Design 02

Design 03

## Measuring angle using Protractor

Suppose you need to find below angle measurement \angle AOB

Do the following steps:

(A) Place the vertex O at the center of protractor

Observe how the vertex is placed just at the center of protractor.
Yo have to do the same otherwise the measurement will be incorrect.

Base of angle is at the right side of protractor.
So we count angle from the right starting from zero degree.

Find the angle where second arm is located

You can see that second arm is at number 30.
hence \angle AOB is 30 degree.

This is how we measure angles using protractor.
Let us see some other examples.

Example 02
Find the angle of below image

(a) Place the vertex O at the center of protractor

(b) Base OA is at the right, so start counting angle from right side.
Find the angle where second arm is located

You can see that arm B is located at 120 degree.
hence \angle AOB is 120 degree.

Example 03
Find the angle measurement \angle AOB

(a) Place the vertex O at the center of protractor

(b) Base OA is at the left of protractor so we count angle from left side
Find the angle where second arm OB is located

You can see that second arm is at 50 degree.
Hence \angle AOB = 50 degree

Example 04
Find angle measure of \angle AOB

You can see that the angle is not horizontally inclined.
So you have to take care while taking measurement

Do the following steps

(a) Place the vertex O at the center of protractor as shown below

(b) Find the angle at second arm of AOB
Start counting protractor angle from A to B

You can see that second arm is at 80 degree.
Hence \angle AOB = 80 degree

i hope you understood how to measure the given angle.
Let us learn how to draw any angle using protractor.

## How to draw angles using Protractor

Take out pencil and paper and draw angles taking below instructions

Example 01
Draw 30 degree angle using protractor

Do the following steps
(a) Mark point O in the paper and place protractor as shown below

This point O will be the Vertex of our angle.
See how protractor is placed such that point O is at the protractor’s central joint

(b) Draw base arm of the angle
We have drawn towards the right side of protractor

(c) Mark 30 degree point from the right and name it Point B
Now join point O and point B

Angle \angle AOB = 30 degree is competed

Example 02
Draw 45 degree angle using protractor

Do the following steps:

(a) Mark point O in the paper and place protractor as shown below

(b) Draw the base arm of the angle

(c) From the left, mark point B on 45 degree and then join OB

Remove the protractor and we will get [/latex] AOB = 45 degree