How do you find int x*secxdxxsecxdx?

1 Answer
Nov 29, 2016

That cannot be evaluated by introductory level functions.

Explanation:

The integral involves the Polylogarithm function Li_2(x) = sum_(k=1)^oo x^k/k^2Li2(x)=k=1xkk2.

WolframAlpha gives

int x secx dx = i(Li_2(-ie^(ix))-Li_2(ie^(ix)))+x(ln(1-ie^(ix))-ln(1+ie^(ix))) +Cxsecxdx=i(Li2(ieix)Li2(ieix))+x(ln(1ieix)ln(1+ieix))+C

You can read more about the polylogarithm here: http://mathworld.wolfram.com/Polylogarithm.html

and here: https://en.wikipedia.org/wiki/Polylogarithm