code: public void mutableMultiply(double c, double d)
      {
          double newR = this.real*c-this.imag*d;
          double newI = this.imag*c+this.real*d;
          this.real = newR;
          this.imag = newI;
      }
docs: Alters this complex number as if a multiplication of another complex number was performed.
  @param c the real part of the other number
  @param d the imaginary part of the other number