Reference: ln

ln(x) is the natural logarithm, i.e. the inverse of the exponential function exp(x). x is a real or complex number.

For a complex number z,

ln(z) = ln(|z|) + i⋅arg(z)

where the argument arg(z) ∈ ]-π, π] and i is the imaginary unit, i.e. i^2 = -1.