Question

How do you calculate `cos((3pi)/2)`?

Answer 1

If we consider the goniometric circle, that is a circle centered in the origin of axes with radius `1`, a point that lies on it has the coordinates: `(cosalpha,sinalpha)`, where `alpha` is the angle (in radians) that the radius makes with the positive real axis Ox.

Since `alpha=3/2pi`, than the point has the coordinates `(0,-1)`, and so `cos(3/2pi)=0`.