# Need help understanding proof of natural log integrals

1. Nov 17, 2011

### annoying

[PLAIN]http://img31.imageshack.us/img31/9004/screenshot20111117at720.png [Broken]

Proofs always get to me for some reason. It's like other problems I can do, but when it comes to proofs I don't know what to put. Can anyone show me steps?

Thank you

Last edited by a moderator: May 5, 2017
2. Nov 18, 2011

### Pablo Antuna

Here you need to prove an identity. So, start with one side of the equation and arrive at something. Then start messing with the other side and try to reach that same something.

If you have already proved the product rule, this little trick may come in handy:

$$\frac{1}{x}=\frac{1}{x}^2x[\tex] 3. Nov 18, 2011 ### HallsofIvy Staff Emeritus You want to look at [tex]\int_1^{1/x} \frac{1}{t}dt$$

Try the substitution u= xt.