# Primitive of Reciprocal of Root of x squared minus a squared

## Theorem

### Inverse Hyperbolic Cosine Form

$\displaystyle \int \frac {\d x} {\sqrt {x^2 - a^2} } = \cosh^{-1} {\frac x a} + C$

### Logarithm Form

$\displaystyle \int \frac {\d x} {\sqrt {x^2 - a^2} } = \map \ln {x + \sqrt {x^2 - a^2} } + C$