# Thread: volume revolved around x-axis

1. ## volume revolved around x-axis

volume of
$y=x^2$ and y=4 rotated about the x-axis

2. Originally Posted by yoman360
volume of
$y=x^2$ and y=4 rotated about the x-axis
washers ...

$R = 4$

$r = x^2$

3. Originally Posted by skeeter
washers ...

$R = 4$

$r = x^2$
ok this is what i did

$int_0^2 16-x^4 dx$

integrate i get

$\frac{128 \pi}{5}$

correct?

4. Originally Posted by yoman360
ok this is what i did

$int_0^2 16-x^4 dx$

integrate i get

$\frac{128 \pi}{5}$

correct?
That's just half the volume

$V=\int_{-2}^2\pi(16-x^4) dx=2\int_0^2\pi(16-x^4) dx$