Aspects

vs

Cos

Cos is short for cosine, mathematical trigonometric function of an angle

Sqrt

`sqrt` function returns the positive square root of a number in several programing languages.

Others

"In term of speed square rooting is easy a few arithmetical operations for some newton-like method but it is not clear what asin does probably quite costly cos is likely to be one order of magnitude slower than sqrt and thus one square root is likely to be quickier than those two transcendental function calls"

from question "Best way to get cos(a) from sin(a)"