# Primitive of Reciprocal of Root of x squared plus a squared/Mistake

## Source Work

Appendix $7$: Integrals

## Mistake

$\ds \int \frac {\d x} {\sqrt {a^2 + x^2} } = \dfrac 1 a \tan^{-1} {\frac x a}$

## Correction

$\ds \int \frac {\d x} {a^2 + x^2} = \dfrac 1 a \tan^{-1} {\frac x a}$