Finding Volume using integration

  • Thread starter Mcbrown108
  • Start date
  • #1

Homework Statement


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


Homework Equations


Probably disk method i would assume:
V=pi*int((f(x)^2) dx from bounds a to b


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.
 
Last edited:

Answers and Replies

  • #2
tiny-tim
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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! :smile:

Isn't that for rotation about the x-axis? :cry:
 
  • #3
Oh yeah. so then would i change my bounds to a=-.9 b=.9
 
  • #4
that doesnt seem to work either
 
  • #5
tiny-tim
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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. :smile:
 
  • #6
So i should plug in the given x's to get y's for my bounds?
 
  • #7
tiny-tim
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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! :smile:
 

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