# Finding Volume using integration

by Mcbrown108
Tags: integration, volume
 P: 6 1. The problem statement, all variables and given/known data Find the volume of the solid formed by rotating the region enclosed by: (e^(1x)+2)/y=0/x=0/x=.9 about the y axis 2. Relevant equations Probably disk method i would assume: V=pi*int((f(x)^2) dx from bounds a to b 3. The attempt at a solution V= pi*int(e^(1x)+2)^2) a=0 b=.9 v=pi*int(e^(2x)+4) a=0 b=.9 v=pi*(1/2e^(2x)+4x) v=pi*(1/2e^(2(.9))-(1/2e^0)+(4(.9) v=pi*(3.025)-(1/2)+3.6 v=6.125pi But my answer is not correct.
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P: 26,148
 Quote by Mcbrown108 Find the volume of the solid formed by rotating the region enclosed by: (e^(1x)+2)/y=0/x=0/x=.9 about the y axis … V= pi*int(e^(1x)+2)^2) a=0 b=.9
Hi Mcbrown108!

Isn't that for rotation about the x-axis?
 P: 6 Oh yeah. so then would i change my bounds to a=-.9 b=.9
 P: 6 Finding Volume using integration that doesnt seem to work either
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P: 26,148
 Quote by Mcbrown108 Oh yeah. so then would i change my bounds to a=-.9 b=.9

Your discs should be "horizontal" discs, centred on the y-axis.
 P: 6 So i should plug in the given x's to get y's for my bounds?