# Integration by Substitution

1. Oct 1, 2007

### markyp23

1. The problem statement, all variables and given/known data

2. Relevant equations

None. Well, dx=du/cosx

3. The attempt at a solution

I've substituted it in, got new values for the limits but I have u^-1 on the bottom and so can't integrate it from my current knowledge. Basically I'm stuck with:

Integration of u^(-1) du with limits of 1 and 2.

Any help appreciated. Apologies for not being able to work the Latex system.

2. Oct 1, 2007

### arildno

Seriously, you haven't encountered the derivative of the natural logarithm yet?

3. Oct 1, 2007

### markyp23

I have but I thought it had to be a linear expression to use the natural log. It did cross my mind though - this is what to do, then?

4. Oct 1, 2007

### arildno

What do you mean by a "linear expression"??

5. Oct 1, 2007

### markyp23

Something of the form (ax+b).

Decided to assume that (u) is in that form and so worked it through. Is ln(2) the final answer?

6. Oct 1, 2007