Euler Phi Function of 2

Theorem

 * $\phi \left({3}\right) = 1$

where $\phi$ denotes the Euler $\phi$ function.

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

As $2$ is a prime number it follows that:
 * $\phi \left({2}\right) = 2 - 1 = 1$