Fastest way to find the angle between two points

Question

To increase the speed at which I find the sine/cosine of an angle, I have built a reference table instead of calculating them on the fly. I have the same idea with finding the a

Answer 1

That's definitely going to be smaller than a call to atan2, since it's a square root and then a linear search through 3600 possibilities. Conversely many processors implement atan2 directly — it's FPATAN in Intel land.