# [SOLVED] Integration difficulty

• Aug 7th 2007, 01:40 AM
bellycan
[SOLVED] Integration difficulty
I can't get my head round this one:

int (1/x^2)*e^(1/x^2)

I know I need to use substitution but if I use u=1/x the derivative doesn't seem to help and the same if I use u=1/x^2

Any help appreciated
• Aug 7th 2007, 06:06 AM
ThePerfectHacker
Quote:

Originally Posted by bellycan
I can't get my head round this one:

int (1/x^2)*e^(1/x^2)

I know I need to use substitution but if I use u=1/x the derivative doesn't seem to help and the same if I use u=1/x^2

Any help appreciated

Let $\displaystyle t=1/x$ then,
$\displaystyle -\int e^{t^2}dt$

Which is not "doable".
• Aug 7th 2007, 07:33 AM
qpmathelp
is it a definite integral
Quote:

Originally Posted by bellycan
I can't get my head round this one:

int (1/x^2)*e^(1/x^2)

I know I need to use substitution but if I use u=1/x the derivative doesn't seem to help and the same if I use u=1/x^2

Any help appreciated

if you have 0 to infinity as limits you might end up with the gamma integral
after suitable substitutions