[Game] mathematical and physical algorithms in Game Development: Angle vs radian

We usually use a Cartesian coordinate system. The corner points are usually (0, 0), that is, the origin. The initial side is in the positive Half Axis of the X axis, and the final side is in an angle with the initial side.
The initial side is clockwise and the clockwise rotation is inverse.

Mathematical representation:
Angle: Degree = radian * 180/π

Radian: radian = degree * π/180

π ≈ 3.141592654

For example, 120 Tib is converted to 2 π/3 radians.

Computer Implementation:
# Define radtodeg 57.29577951f
# Define degtorad 0.017453293f

 

Post from http://www.cnblogs.com/HelloCG/archive/2009/01/14/1375878.html