Re: [math-fun] x>0 and y>0

atan2(y,x)/pi<1/2 Don't laugh too hard; as floating point and GPU's become ubiquitous, this approach may actually be as fast as some other approaches -- particularly in very deeply pipelined units. Of course, it would work somewhat more reliably if atan2(y,x)/pi were the primitive instead of atan2(y,x) itself.