Euler Phi Function of Non-Square Semiprime/Proof 1

Proof
As $p$ and $q$ are distinct prime numbers, it follows that $p$ and $q$ are coprime.

Thus by Euler Phi Function is Multiplicative:
 * $\map \phi n = \map \phi p \, \map \phi q$

From Euler Phi Function of Prime:
 * $\map \phi p = p - 1$
 * $\map \phi q = q - 1$

Hence the result.