pow method
Raise the complex number to the integer power n.
Use De Moivre's formula: (re^(itheta))^n = r^n * e^(intheta).
Implementation
Complex pow(int n) {
if (n == 0) return one;
final double rPow = math.pow(_modulus, n).toDouble();
final double angle = n * _theta1;
return Complex.polar(rPow, angle);
}