Question

Find the volume of a solid. x=2 sqroot of (y) x=0 y=9 about the y axis

Answer 1

its a 3-D question right?

Answer 2

yes

Answer 3

don't u think there should be a z co=ordinate as well

Answer 4

Use the disc method.
\[V = \pi \int\limits_{a}^{b} f(y)^{2} dy\]
\[f(y) = 2\sqrt{y}\]
\[V = \pi \int\limits\limits_{0}^{9} (2\sqrt{y})^{2} dy = \pi \int\limits_{0}^{9} 4ydy\]

Answer 5

did that help?

Answer 6

ohhhh its easy

Answer 7

yess.. thanks

Answer 8

if it was about the x-axis, just use f(x) and integrate w/ respect to x

Answer 9

yea,, thats waht confuses me... but i am gettting it