roots of complex numbers

[Joseph Colannino]

I have had to create a special program to take the roots of complex numbers since most of the time, the HP's root function fails. For example, the cube root of -11 + 2i is 1 + 2i, yet EVAL cannot simply the function and NUM gives an error message "NUM ERROR: Bad Argument Type." Inextricably, the calculator correctly evaluates the square root of this complex number. Since the evaluation of complex roots is relatively simple, why will the calculator not evaluate many of them?