Let us go through the illustrations of angles given below.
We see angles around us all the time.
In all of the above diagrams, we can see two rays have common endpoint.
| An angle is a figure formed by two rays with same initial point. |
What are the parts of an angle?
BC and BA have the common endpoint B.
Common end point of the two rays is called the vertex of an angle
Ray BC and Ray BA are called the arms of the angle
Angle ABC is represented as <ABC
| Middle letter represents the vertex of the angle The plural of vertex is vertices |
How to measure an angle?
If we rotate a ray OP about O, it makes angles of increasing magnitudes. If
we rotate until it takes position OQ, then measure of <POQ is 90-degrees.
It is called right angle. If we rotate it to ray OR, then measure of <POR is
180 degrees. It is called straight angle. If we continue to rotate until it takes original position OP, then the measure of angle is 360 degrees. 360-degree angle is called complete angle.
How to measure angles using protractor?
Steps to measure an angle.
To find the measure of the below angle,
Step 1. Place the center point of the protractor on the vertex of the angle.
Step 2. Place one of the arms along the base line (do not shift the protractor from the vertex).
Step 3. Look at which scale the base line arm points to 0 degrees. Here it is in inner scale.
Step 4. Look at the scale where the other arm of the angle points in the inner scale. It is 62 degrees in the above diagram.
Measure of the angle is 62 degrees
Find the measure of the following angles.
a)
b)
