Calculus help

1. Sep 14, 2004

nomi

2. Sep 14, 2004

Pyrrhus

There's something wrong, you shouldn't do u = e^-x dx, only u = e^-x and when you say -du = e^-x dx, you have to substitute it completely in the integral i mean -\int { tan(u)du}

3. Sep 14, 2004

nomi

i think i know what you're saying, but i took the -1 out since its a constant.

4. Sep 14, 2004

Pyrrhus

that's ok, i'm talking about your substitution... You should not pick u = e^-x dx, why without dx? you will know why not later, and if you have a -du = e^-x dx, you should not have -\int {tanu dx} you should have -\int {tanu du} see what i mean?, remember in your du you have the dx.

5. Sep 14, 2004

nomi

oh sorry yeah that is a careless mistake, but other than the dx it's ok?

6. Sep 15, 2004

NateTG

Aside from that it looks good to me.

7. Sep 15, 2004

nomi

ok thanks a lot guys :)