The Calculator normally "prefers" rectangular complex numbers in the sense that rectangular form is used when the proper form can not be decided from the input. This might happen by multiplying a rectangular number by a polar one, by taking the square root of a negative real number, or by entering ( 2 SPC 3 ).
The m p (
calc-polar-mode) command toggles complex-number
preference between rectangular and polar forms. In polar mode, all
of the above example situations would produce polar complex numbers.