Why is the implementation of computing both sine and cosine at the same time about the same speed as just computing one of them?

Question

Was messing around with C and found this quirk. How does this function work so quickly? How is it implemented?

In: Mathematics

Answer 1

The ELI5 answer is because sin and cos have the same values just 90 degrees out of phase. Just look at a graph of sin and a graph of cos to see what I mean.