Integration problem

**coolguy99** · April 6th 2009, 06:40 PM

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

**TheEmptySet** · April 6th 2009, 06:46 PM

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 $2x-5=\tan(\theta) \implies 2dx=\sec^{2}(\theta)d\theta$

**Chris L T521** · April 6th 2009, 06:46 PM

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.

**Reckoner** · April 6th 2009, 06:47 PM

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!

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