degrees to radians and radians to degrees

360 deg = 2pi rads
1 rads = 360 deg / 2pi = 57.30 deg
1 deg = 2pi rads / 360 = pi rads / 180 = 0.017 rads

Ex.1

convert 150 deg to radians.

1 deg = pi rads / 180
150 deg = 150 pi rads / 180 = 
150 deg = 15 pi rads / 18 = 
150 deg = 5 pi rads / 6 = 
5/6 *  pi rads

Ex. 2

convert -45 deg to radians

1 deg = pi rads / 180
-45 deg = -45 / 180 pi rads
-45 deg = - 9 / 36 pi rads
-45 deg = - 3 / 12 pi rads
-45 deg = -1 / 4 pi rads deg