Math.sin returns unexpected results

Question

Math.sin(Math.PI) returns 1.2246467991473532E-16

Math.sin(-Math.PI) returns -1.2246467991473532E-16

But mustn't it return zeros?

Though sin from 3.14 and 3.15 are correct.

Answer 1

Math.PI is not "exactly" π, it's just a roughly-16-digit approximation of π (3.141592653589793). No floating point format can store π exactly. That's why you don't get the exact zero.