== Product formula relation == 

 "The Dirichlet series that generates the Möbius function is the (multiplicative) inverse of the Riemann zeta function 

 \sum_{n=1}^\infty \frac{\mu(n)}{n^s}=\frac{1}{\zeta(s)}. 
 This is easy to see from its Euler product" 

 Why is it clear? Am i being stupid here?