# Integration problem

• Apr 6th 2009, 07:40 PM
coolguy99
Integration problem
I'm blanking out on this one..

integral from -1 to 3 of..

sq.root(1 + (2x-5)^2)

Don't need you guys to do it, just give me a hint on how to go about it.. this is probably easy, I'm just blanking out
• Apr 6th 2009, 07:46 PM
TheEmptySet
Quote:

Originally Posted by coolguy99
I'm blanking out on this one..

integral from -1 to 3 of..

sq.root(1 + (2x-5)^2)

Don't need you guys to do it, just give me a hint on how to go about it.. this is probably easy, I'm just blanking out

let $2x-5=\tan(\theta) \implies 2dx=\sec^{2}(\theta)d\theta$
• Apr 6th 2009, 07:46 PM
Chris L T521
Quote:

Originally Posted by coolguy99
I'm blanking out on this one..

integral from -1 to 3 of..

sq.root(1 + (2x-5)^2)

Don't need you guys to do it, just give me a hint on how to go about it.. this is probably easy, I'm just blanking out

Let $2x-5=\tan\theta$. It should be straightforward from there. :D
• Apr 6th 2009, 07:47 PM
Reckoner
Quote:

Originally Posted by coolguy99
I'm blanking out on this one..

integral from -1 to 3 of..

sq.root(1 + (2x-5)^2)

Don't need you guys to do it, just give me a hint on how to go about it.. this is probably easy, I'm just blanking out

$\int_{-1}^3\sqrt{1+(2x-5)^2}\,dx$

Substitute $2x-5=\tan\theta\Rightarrow dx=\frac12\sec^2\theta\,d\theta.$

Edit: Curses! I've been beaten!