# Math Help - Solving for the Area under a Curve rotated around the x-axis.

1. ## [SOLVED]Solving for the Area under a Curve rotated around the x-axis.

I know how to use the shell method for this problem. But I'm not sure how to solve it using disk or washer. I know you solve for X which gives you X=(Y)^(.25).

The parameters are. Y=x^4 x=0 y=81

I know is the equation for washer method.

This mean . Now I'm lost? What's the Big R and Little r now.
Big R= 81-0?
Little r= (Y^(.25))-0?

2. Originally Posted by Bracketology
I know how to use the shell method for this problem. But I'm not sure how to solve it using disk or washer. I know you solve for X which gives you X=(Y)^(.25).

The parameters are. Y=x^4 x=0 y=81

I know is the equation for washer method.

This mean . Now I'm lost? What's the Big R and Little r now.
Big R= 81-0?
Little r= (Y^(.25))-0?
rotation of the region about the x or y axis?

3. Around the x-axis. Would I use disk method?

4. Originally Posted by Bracketology
Around the x-axis. Would I use disk method?
yes, disks ...

$\displaystyle V = \pi \int_0^3 81^2 - (x^4)^2 \, dx$

5. Oops....For some reason I thought the x-axis was the y-axis. Thanks for your help.