# help with an integral involving the exp function

• Oct 19th 2009, 03:28 AM
xnr
help with an integral involving the exp function
Hi everyone

I've been dealing with a rather difficult (at least for me) integration problem which I am not able to find in integration tables I've been consulting.
After a variable transformation I ended up with the following sets of integrals:

$\displaystyle \int e^{y}/y^{2}dy$ from 0 to t (t is not infinity) and

$\displaystyle \int e^{y}/y^{3}dy$ also from 0 to t

I ended up with these starting from

$\displaystyle \int A*e^{B/(C-D*x)}*xdx$ (A,B,C and D are constants) from 0 to infinity and using the transform

$\displaystyle y=B/(C-D*x)$

any ideas?

thanks
xnr
• Oct 19th 2009, 03:42 AM
harbottle
You should be able to use integration by parts to get the indefinite integrals - eg for the first, apply once to get the integral e^y/y, then integrating this by parts gives you an integral of e^y * ln y. Apply parts once more and you should be able to get the result