General Periodicity Property/Corollary

Theorem
Let $f: \R \to \R$ be a real function.

Then $f$ is periodic with period $L$ :
 * $f \left({x \bmod L}\right) = f \left({x}\right)$

for all $x \in \R$, where $x \bmod L$ is the modulo operation.

Necessary Condition
Let $f: \R \to \R$ be a real periodic function with period $L$, then:

Sufficient Condition
Let $f: \R \to \R$ be a real function such that for all $x \in \R$:
 * $f \left({x \bmod L}\right) = f \left({x}\right)$

Let $n = \left \lfloor {\dfrac x L}\right \rfloor$.

Then: