Posted by **Ted** on Tuesday, July 24, 2012 at 10:35am.

The area is bounded by y= x^3, x= 2 is rotated around the x-axis. Find the volume using calculus.

- Calculus -
**Reiny**, Tuesday, July 24, 2012 at 11:45am
I will assume that the x-axis was the other boundary of the region we are rotating

Using discs ...

radius = y = x^3

volume = π∫ y^2 dx from 0 to 2

= π∫ x^6 dx from 0 to 2

= π[ (1/7)x^7 ] from 0 to 2

= π((1/7)(2^7) - 0 ]

= 128π/7

- Calculus -
**Damon**, Tuesday, July 24, 2012 at 11:47am
It is not clear to me how you would do this without using calculus :)

Graph a sketch of it first. The corners are at (0,0) , (2,0) and (2,8)

Lets add up a bunch of thin cylinders with axes along x axis

volume of thin cylinder = pi y^2 dx

so

in from x = 0 to x = 2 of pi (x^3)^2 dx

or pi x^6 dx

or pi (1/7)x^7

or 1/7 (128)

about 18.3

- times pi -
**Damon**, Tuesday, July 24, 2012 at 11:49am
I forgot to multiply by pi

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