Primitive of Reciprocal of a squared minus x squared/Logarithm Form 1

Theorem

 * $\displaystyle \int \frac {\mathrm d x} {a^2 - x^2} = \frac 1 {2 a} \ln \left({\frac {a + x} {a - x} }\right) + C$

where $x^2 < a^2$.