Primitive of Reciprocal of x by Root of x squared plus a squared/Reciprocal Logarithm Form

Theorem

 * $\displaystyle \int \frac {\d x} {x \sqrt {x^2 + a^2} } = \frac 1 a \map \ln {\frac x {a + \sqrt {x^2 + a^2} } } + C$

Also see

 * Primitive of Reciprocal of $x \sqrt {x^2 - a^2}$
 * Primitive of Reciprocal of $x \sqrt {a^2 - x^2}$