Definition:Reciprocal

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

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

The real function:


 * $f: \R \setminus \left\{{0}\right\} \to \R: f \left({x}\right) = \dfrac 1 x$

is called the reciprocal function.

Warning
Note the domain of the function $f: \R \setminus \left\{{0}\right\} \to \R$.

That is, $\dfrac 1 0$ is not defined.

Also see

 * Harmonic Numbers
 * Natural Logarithm