how Riemann pass from the Euler product to the expression with exponential...

Question

In his famous article Riemann about Zeta hypothesis start from the Euler's product and rewrite it as an integral. Can someone explain me how this passage is done, because, it's evident for the great Riemann but not for me …in other word how Riemann does to pass from the first to the second equation?

Answer 1

Is this what you are looking for? At the link is a detailed proof following the approach outlined in Riemann's paper.