## Fey Group Title Calculus: The region in the first quadrant bounded by the graphs of the equations y=(1/x), x=1, x=2, is revolved around the x-axis. Use the shell method to find the volume of the resulting solid. one year ago one year ago

1. Fey Group Title

I need help finding h(y),,,, (Height)

2. klimenkov Group Title

|dw:1360447641218:dw|

3. Fey Group Title

m,,, ok, I know the bounds are [1,2], the radius is y.... now, the height i want to say (1/y)-1????

4. klimenkov Group Title

$$V=\pi\int \limits_1^2y^2dx$$

5. Fey Group Title

The shell method uses the 2(pi) at the beginning. Can u explain how u got that answere?

6. klimenkov Group Title

Yes. You have to understand what integral means. This solid consists of many little cylinders like on the pic|dw:1360448107971:dw| The volume of the cylinder is $$\pi R^2h$$, on the pic $$R$$ is $$y(x)$$ and $$h$$ is $$dx$$. We want the whole solid, so we sum the volumes of this small cylinders and get the volume of the solid as an integral.

7. Fey Group Title

well,,, im still not getting the right answere. its suppoased to be (pi)/2....

8. klimenkov Group Title

You have to calculate the integral I wrote correctly.

9. Fey Group Title

Oops. I made a mistake xD Ok, got it thanks.

10. klimenkov Group Title

You are welcome.