Not sure if this is the right place to post this but could someone help get me started and point me in the right direction.

Given:

x= r(cosu+isinu) andy= t(cosv+isinv)

Prove that the modulus of (xy) is the product of their moduli. Showeachstep of your proof.

Prove that the amplitude of (xy) is the sum of their amplitudes. Showeachstep of your proof.

If you know of any place I could visit to understand this better I would be grateful.

Thanks