Hello vramirezThere are three vital things that you need to complete the proof:
- (1)
- (2)
- (3)
So, you simply multiply by by expanding the brackets, but leave the and outside:
, by re-arranging the order of the terms, and using (1)
, using (2) and (3)
, where and
And this is a complex number whose modulus is , and amplitude , where product of the moduli of and , and sum of their amplitudes.
Grandad