Register to reply

Finding Volume using integration

by Mcbrown108
Tags: integration, volume
Share this thread:
Mcbrown108
#1
Jul3-08, 02:30 PM
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.
Phys.Org News Partner Science news on Phys.org
Mysterious source of ozone-depleting chemical baffles NASA
Water leads to chemical that gunks up biofuels production
How lizards regenerate their tails: Researchers discover genetic 'recipe'
tiny-tim
#2
Jul3-08, 02:47 PM
Sci Advisor
HW Helper
Thanks
tiny-tim's Avatar
P: 26,148
Quote Quote by Mcbrown108 View Post
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?
Mcbrown108
#3
Jul3-08, 02:49 PM
P: 6
Oh yeah. so then would i change my bounds to a=-.9 b=.9

Mcbrown108
#4
Jul3-08, 03:22 PM
P: 6
Finding Volume using integration

that doesnt seem to work either
tiny-tim
#5
Jul3-08, 03:47 PM
Sci Advisor
HW Helper
Thanks
tiny-tim's Avatar
P: 26,148
Quote Quote by Mcbrown108 View Post
Oh yeah. so then would i change my bounds to a=-.9 b=.9
It's not your bounds that are wrong it's your discs.

Your discs should be "horizontal" discs, centred on the y-axis.
Mcbrown108
#6
Jul3-08, 04:08 PM
P: 6
So i should plug in the given x's to get y's for my bounds?
tiny-tim
#7
Jul3-08, 05:01 PM
Sci Advisor
HW Helper
Thanks
tiny-tim's Avatar
P: 26,148
Quote Quote by Mcbrown108 View Post
So i should plug in the given x's to get y's for my bounds?
I've no idea what that means, but I'm going to guess the answer is "YES!!"

Go for it!


Register to reply

Related Discussions
Finding volume by integration Calculus & Beyond Homework 8
Integration Volume Calculus & Beyond Homework 4
Volume by integration Calculus & Beyond Homework 4
Volume integration Introductory Physics Homework 3
Finding the Volume of a solid by integration Calculus 8