Rudin 3.48 cauchy product

1. Jul 15, 2012

jecharla

Rudin motivates this formula by multiplying two power series and then setting z = 1 and somehow obtaining the cauchy product formula. But I am not following how he does this at all. Can anyone help me understand this?

2. Jul 15, 2012

jecharla

Nevermind I figured it out!