The measure of an angle is the amount of rotations required to get to the terminal side from the initial side. A common measure of an angle is derived by placing its vertex at the center of a circle of some fixed radius.
There are two commonly used measurements for angles: Degrees and Radians
Sexagesimal System: (Degree, Minute and Second)
If the initial ray rotates in anti-clockwise direction in such a way that it coincides with itself, the angle then formed is said to be of degrees ().
One rotation (anti-clockwise) =
rotation (anti-clockwise) = is called a straight angle
rotation (anti-clockwise) = is called a right angle.
1 degree () is divided into minutes () and 1 minute () is divided into seconds (). As this system of measurement of angles owes its origin to the English and because, and multiplies of and , so it is know as English system or Sexagesimal system.
Thus rotation (anti-clockwise) =
One degree () =
One minute () =
Conversion from to a decimal form and vice versa.
Example: Convert to decimal form.
Example: Convert to the form