2.1.994 Part 4 Section 188.8.131.52, IMLN
a. The standard does not specify what happens if complex-number is zero.
Office returns #NUM! if complex-number is zero.
b. The standard does not fully specify how the angle θ is calculated.
Excel calculates imln using the following mathematical formula:
θ = ATAN2(x,y) calculated according to the formula in ATAN2 (“[ECMA-376] Part 4 §184.108.40.206; ATAN2”)