Something I've noticed that no one has ever been able to sufficiently explain to me is taking the sin of multiples of 2-pi. Sin 6pi, 8pi, 12pi. You get silly answers. For example, sin(6pi) gives you -4*10^-13 instead of 0. I've never been able to get a satisfactory explanation. Most people say "that's weird, must be how it computes it or something". A teacher said something about precision. Does anyone understand WHY it does this? Anything other than an 84 you get 0. Even my crappy $10 scientific calculators give back 0.