Definition:Inverse Mapping

Definition
If the inverse $f^{-1}$ of a mapping $f$ is itself a mapping, then it is called the inverse mapping of $f$.

Thus, from the definition of a mapping, for $f^{-1}$ to be the inverse mapping of $f$:


 * $\forall y \in T: \left({x_1, y}\right) \in f \land \left({x_2, y}\right) \in f \implies x_1 = x_2$

and


 * $\forall y \in T: \exists x \in S: \left({x, y}\right) \in f$

When $f^{-1}$ is a mapping, we say that $f$ has an inverse mapping or that $f$ is an invertible mapping.

Also see

 * Bijection iff Inverse is Bijection, where is shown that $f^{-1}$ is a mapping iff $f$ is a bijection, and that $f^{-1}$ it itself a bijection.


 * Inverse of Bijection