What is Straight Angle?
The measure of an angle is the amount of turn or rotation of a point from one arm to another along its vertex.
When the arms of the angle lie in the opposite direction, they form a straight angle. The angles make a straight line through the vertex.
A straight angle is also called ‘flat angle’.
In the picture, OX and OY are the arms of an angle. The common point O where the rays meet is called the vertex.
How to represent a straight angle?
There are various ways to represent straight angles as per the measurement system.
- It is written as 180°
- It is also written as π
All angles given in the picture are straight angles.
Properties of a straight angle
- A straight angle is formed by rotating one ray by 180°with respect to another ray.
- In a straight angle, the angle rays face in the opposite directions.
- A straight angle reverses the direction of a point
- A straight angle is exactly half of a revolution.
- A straight angle can also be formed by adding two right angles.
Drawing a straight angle using a protractor
- Draw a straight-line OA, with an arrowhead at A.
- Now keep the protractor on this line such that the baseline of the protractor is aligned over OA. The A should be pointing towards the 0°of the protractor.
- Start from 0° and move towards 180° marking of the protractor. On arriving at 180°, mark a point B on the paper.
- Join the vertex of the line OA with the point B. the second ray OB will have the arrowhead at B.
Straight angles in real life
- The inclined plane of a staircase represents a straight angle.
- The straight angle of a see-saw.
– Straight angles look like a straight line, but it has two arms. On the other hand, a straight line has only one arm that points in one direction.