The independent variables of the trigonometric function are unitized. They are degrees (°: Degree) and radians (Radian). The correspondence between the two functions is very easy to remember. It is only necessary to grasp the transformation of 2π = 360° (a circumferential angle equal to 360 degrees). Just fine.

From this formula, it is possible to directly derive 30°=π/6, 45°=π/4, 60°=π/3, 90°=π/2, and so on.