PHASE function
Description
PHASE(A) returns the phase angle (or angular component) of the complex number A, expressed in radians. This is the Excel IMARGUMENT function.
The argument A can be a real number, a complex number or a matrix. When it is a matrix, the function returns a matrix with the same dimensions and with the PHASE function applied to all elements.
$$ phase(a+bi) = asin\left(b / abs(a+bi) \right) $$
Visual representation
Example
PHASE(2+3i) returns 0.982793723
PHASE(pi()*1i) returns 1.570796327
PHASE(3) returns 0.