code: public ComplexDouble divi(ComplexDouble c, ComplexDouble result) {
      double d = c.r * c.r + c.i * c.i;
      double newR = (r * c.r + i * c.i) / d;
      double newI = (i * c.r - r * c.i) / d;
      result.r = newR;
      result.i = newI;
      return result;
    }
docs: Divide two complex numbers, in-place
  
  @param c      complex number to divide this by
  @param result complex number to hold result
  @return same as result