# Primitive of Arcsecant of x over a over x

## Theorem

 $\displaystyle \int \frac {\operatorname{arcsec} \frac x a \ \mathrm d x} x$ $=$ $\displaystyle \frac \pi 2 \ln \left\vert{x}\right\vert + \sum_{k \mathop \ge 0} \frac {\left({2 k + 1}\right)!} {2^{2 k} \left({k!}\right)^2 \left({2 k + 1}\right)^3} \left({\frac a x}\right)^{2 k + 1} + C$ $\displaystyle$ $=$ $\displaystyle \frac \pi 2 \ln \left\vert{x}\right\vert + \frac a x + \frac 1 {2 \times 3 \times 3} \left({\frac a x}\right)^3 + \frac {1 \times 3} {2 \times 4 \times 5 \times 5} \left({\frac a x}\right)^5 + \frac {1 \times 3 \times 5} {2 \times 4 \times 6 \times 7 \times 7} \left({\frac a x}\right)^7 + \cdots + C$