Primitive of Root of x squared minus a squared/Logarithm Form

Theorem

 * $\displaystyle \int \sqrt {x^2 - a^2} \ \mathrm d x = \frac {x \sqrt {x^2 - a^2} } 2 - \frac {a^2} 2 \ln \left({x + \sqrt {x^2 - a^2} }\right) + C$