# Math Help - exponential integral

1. ## exponential integral

not quite sure how to do this one:

$\int^2_1 e^{lnu}\frac{1}{u}du$

2. Originally Posted by viet
not quite sure how to do this one:

$\int^2_1 e^{lnu}\frac{1}{u}du$
substitution. let t = ln(u)

3. Note,
$e^{\ln u}=u$

So,
$e^{\ln u}\cdot \frac{1}{u} = \frac{u}{u}=1$

4. Originally Posted by ThePerfectHacker
Note,
$e^{\ln u}=u$

So,
$e^{\ln u}\cdot \frac{1}{u} = \frac{u}{u}=1$
yeah, i missed that. thanks