Also, a circle has radians in it, so any angle + equals that angle.
It's the same as adding 360 degrees, if you do a 360 you are right back where you started, angle x radians + radians = x radians
you can see this by choosing any x value you like, then typing into a calculator sin(x) and (make sure your calculator is in radians and not in degrees)
some suggested values of x that you should try are
so for an integer