Function acosh 

pub fn acosh(x: f64) -> f64

Returns the hyperbolic arc (also called inverse) cosine of x, returning a value in radians. Use it to get the angle from an angle’s cosine in hyperbolic space if x is larger or equal to 1. For values of x lower than 1, it will return 0, in order to prevent [method acosh] from returning @GDScript.NAN.

var a = acosh(2) # Returns 1.31695789692482
cosh(a) # Returns 2

var b = acosh(-1) # Returns 0