Inverse of Inverse of Bijection/Proof 2

Theorem

Let $f: S \to T$ be a bijection.

Then:

$\paren {f^{-1} }^{-1} = f$

where $f^{-1}$ is the inverse of $f$.

Proof

A mapping is a relation.

Thus it follows that Inverse of Inverse Relation can be applied directly.

$\blacksquare$