Definition:Reciprocal

Let $$x \in \reals$$ be a real number such that $$x \ne 0$$.

Then $$\frac 1 x$$ is called the reciprocal of $$x$$.

Note that $$\frac 1 0$$ is not defined.

The real function $$f: \reals - \left\{{0}\right\} \to \reals: f \left({x}\right) = \frac 1 x$$ is called the reciprocal function.