1. ## Integral problem

Hey,
In one of my text books that following equation was written:

My question is .. Where did the x (In the red circle) go to ? Why is it ignored ?

Thanks a lot !

2. ## Re: Integral problem

Originally Posted by MichaelEngstler
Hey,
In one of my text books that following equation was written:
My question is .. Where did the x (In the red circle) go to ? Why is it ignored ?
First it was not ignored. It is part of $dt=\dfrac{dx}{x}$.

Note that the limits of integration also change.

3. ## Re: Integral problem

Can you please explain why dt = dx/x ?

4. ## Re: Integral problem

Originally Posted by MichaelEngstler
Can you please explain why dt = dx/x ?
$t = ln(x) \implies \dfrac{dt}{dx} = \dfrac{1}{x} \implies dt = \dfrac{dx}{x}.$

5. ## Re: Integral problem

Originally Posted by MichaelEngstler
Can you please explain why dt = dx/x ?
$t=\ln(x)$ so $\dfrac{dt}{dx}=\dfrac{1}{x}$ so $dt=\dfrac{dx}{x}$

Thanks a lot