Primitive of Reciprocal of x squared minus a squared/Inverse Hyperbolic Tangent Form

Theorem

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

where $\size x < a$.

Also see

 * Primitive of $\dfrac 1 {x^2 - a^2}$: $\coth^{-1}$ form for the case $\size z > a$