Maths 1- Angle and its Measurement

Directed Angle

The ordered pair of rays together with the rotation of the ray OA to the position of the ray OB is called the directed angle AOB.

If the rotation of the initial arm is anticlockwise then the measure of the directed angle is considered to be positive. If the rotation of the initial arm is clockwise then the measure of the directed angle is considered to be negative.

Angles in standard position

In the rectangular coordinate system an angle with the origin as its vertex and its initial arm along the positive X-axis is called angle in standard position.

Quadrantal Angles

A directed angle in standard position with its terminal arm along X-axis or Y-axis is called a quadrantal angle.

Coterminal angles

Directed angles of different rotation having the same position of initial rays and terminal rays are called coterminal angles.

Difference between any two coterminal angles is always an integral multiple of 360 degrees.

Regular polygon

Polygon in which all angles and all sides are equal is called a regular polygon.