# Applications of Intergration

• Oct 18th 2011, 11:47 AM
kashmoneyrecord3
Applications of Intergration
I've been stuck on a question and need some help.

The question is

Find the volume of the solid obtained by rotating the region bounded by the given curves about the specified line. Sketch the region, the solid, and a typical disk or washer.

y=1/4 x^2 , x=2, y=0 about the y-axis.

So my question is what would the interval of this question be? I thought since it's about the y-axis that we would need to solve for y which I did and got y=1, so i thought the interval would be between 1 and 0. But then i thought to myself it can't be because the question has an x variable to it, so you have to solve for x and find the interval right?

If you didn't understand what I just said let me know and I will try to make it clearer. Please help on this one guys, this is the only question confusing me which is why I can't move onto the next section.

• Oct 18th 2011, 01:05 PM
Youkla
Re: Applications of Intergration
Since it specifically says for you to solve it using disk/washer, then yes, you do have to solve the equation for x in terms of y. Then the integral limits would have to be the y limits which would be from 0 to 1.
• Oct 18th 2011, 01:10 PM
kashmoneyrecord3
Re: Applications of Intergration
thanks a lot bro, but after I get the interval right what would the form be as in like would it be [1/4 x^2]between 0 and 1 or would I have to use the squareroot 4y?
• Oct 18th 2011, 01:23 PM
Youkla
Re: Applications of Intergration
Square root of 4y or, simply 2 times the square root of y.
• Oct 18th 2011, 01:31 PM
kashmoneyrecord3
Re: Applications of Intergration
haha thanks a lot man :D