I came across some weird behavior by math.cos() (Python 3.11.0): >>> import math >>> math.cos(math.pi) # expected to get -1 -1.0 >>> math.cos(math.pi/2) # expected to get 0 6.123233995736766e-17 I suspect that floating point math might play a role in this, but I'm not sure how. And if it did, I'd assume Python just checks if the parameter equaled math.pi/2 to begin with. I found this answer by Jon Skeet, who said: Basically, you shouldn't expect binary floating point operations to be exactly right when your inputs can't be expressed as exact binary values - which pi/2 can't, given that it's irrational. But if this is true, then math.cos(math.pi) shouldn't work either, because it also uses the math.pi approximation. My question is: why does this issue only show up when math.pi/2 is used? Continue reading...
