Calc 3 HW problem help? Integrals

[Undisputed King 10+ year member]

Ok so I have a volume of a curve problem, using the double integrals and such, but I just need help taking an integral of something i forgot how to do. Ok so I need to take the integral of (x/sqrt(1+y^2)) dy from x^2 to 4. I dont really need you to plug in the bounding values, I just need some help on how to take the definite integral of that. Thanks

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[RAM_Designs 5,000+ posts]

I hated this shit in my calc class. Good luck man.

 

[Undisputed King 10+ year member]

Thanks, Anyone? I have a final tomorrow, and its simple Calc 2 stuff thats holding me back.

 

[Supergumby5000 5,000+ posts]

take the sqrt function and write it as (function)^-1/2. it'll make it appear a lot simpler.

(x/sqrt(1+y^2) will look like: (x)(1+y^2)^(-1/2)

see if you can get anywhere with that.

i have a calc III final on wednesday

 

[Undisputed King 10+ year member]

Ok so I get x∫(1+y^2)^(-1/2) dy

But my question is do I use a u subtitution? I had gotten this far, but im pretty much stuck on how to take the integral from there ^^

Good luck on the final man, dont be too sad, cause next semester is Differential Equations, supposed to be better!

 

[Undisputed King 10+ year member]

Oh I got it!

I should instead write it like this:

x∫(1/sqrt(1+y^2))dx

then I get:

x ln(sqrt(1+y^2))

Just thought i'd post it up since u have a final wednesday too.

 

[Supergumby5000 5,000+ posts]

edit.

you got it //content.invisioncic.com/y282845/emoticons/thumbsup.gif.3287b36ca96645a13a43aff531f37f02.gif