Function asin 

pub fn asin(x: f64) -> f64

Returns the arc sine of x in radians. Use to get the angle of sine x. x will be clamped between -1.0 and 1.0 (inclusive), in order to prevent [method asin] from returning @GDScript.NAN.

# s is 0.523599 or 30 degrees if converted with rad_to_deg(s)
var s = asin(0.5)