pub fn cos(x: f64) -> f64
cos x for |x| ≤ 0.25 by its Taylor polynomial through x¹⁰: the truncation error is below 0.25¹² / 12! < 1.3e-16 (see sin).
cos x
|x| ≤ 0.25
x¹⁰
0.25¹² / 12! < 1.3e-16
sin