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:
 * $\phi \left({n}\right) = \phi \left({p}\right) \phi\left({q}\right)$

From Euler Phi Function of Prime:
 * $\phi \left({p}\right) = \left({p - 1}\right)$
 * $\phi \left({q}\right) = \left({q - 1}\right)$

Hence the result.