I'm trying to solve the following integral:
$\int \frac{1}{1+\cot^3(x)}dx$
While the solution can be found in Wolfram Alpha, I am not completely sure how to reduce the above integral to get the solution referenced. Pointers would be appreciated.
I'm trying to solve the following integral:
$\int \frac{1}{1+\cot^3(x)}dx$
While the solution can be found in Wolfram Alpha, I am not completely sure how to reduce the above integral to get the solution referenced. Pointers would be appreciated.
Let $u=\cot(x)$; then $dx = -\frac{1}{u^2+1}du$. Now the integral becomes
$ I = - \int \frac{1}{(u^2+1)(u^3+1)} du $
which can be resolved into partial fractions as:
$ I =- \int \frac{1-2u}{3(u^2-u+1)} + \frac{u+1}{2(u^2+1)} + \frac{1}{6u+6} du $
each sub-integral of which can be readily evaluated.
If you make the change of variables $ x=\arctan(t) $ you get
$ \int \!{\frac {{t}^{3}}{ \left( 1+{t}^{3} \right) \left( 1+{t}^{2} \right) }}{dt}\,. $