- #1
Destroxia
- 204
- 7
Homework Statement
Find the volume of the solid generated by revolving the region bounded by the graphs of the equations about the line x = 5. (Use disk method)
$$ xy = 3, y = 1, y = 4, x = 5 $$
Homework Equations
[/B]
The formula using for disk method is of the form:
$$ \pi \int (r(x/y))^2*(dx/y) $$
The Attempt at a Solution
[/B]
So first I graphed this out, and came up with a region, like so (represented by the white region):
In disk method, when rotating around a vertical axis, the differential of dy is used.
Setting this integral up, our limits are y = 1, to y = 4, as given in the problem statement.
My main question is how do we represent the r in the disk method equation, when the axis is meant to be around x = 5, and not the y-axis.
The best I could think of would be:
$$ \pi \int_{1}^{4} (\frac {y} {3} + 5)^{2} dy $$
However, something tells me this isn't the right approach, because I'm not seeing the logic behind whether or not I should add, subtract, or subtract from the x = 5.
Thank you.