Codomain of Bijection is Domain of Inverse

Theorem
Let $S$ and $T$ be sets.

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

Let $f^{-1}: T \to S$ be the inverse of $f$.

Then the domain of $f^{-1}$ equals the codomain of $f$.

Proof
Follows directly from the definition of domain and codomain:


 * $\Dom f = S$ and $\Cdm f = T$
 * $\Dom {f^{-1} } = T$ and $\Cdm {f^{-1} } = S$

That is:
 * $\Dom {f^{-1} } = T = \Cdm f$

Also see

 * Domain of Bijection is Codomain of Inverse