• Support PF! Buy your school textbooks, materials and every day products Here!

Area betweeen curves

  • Thread starter Aerosion
  • Start date
  • #1
53
0

Homework Statement



This is so basic and yet I'm not getting it.

Find the volume of the solid when the region enclosed is revolved arond the y axis.

[tex] x = \sqrt{1 + y}[/tex]
x=0, y=3

Homework Equations





The Attempt at a Solution



So I first graphed the thing, finding that the enclosed area was between y=1 and y=3. I took the volumne of the equation, or A=pi *[tex]\sqrt{1 + y}^2[/tex]. I then took the integral, pi * [tex]\int_{1}^{3} 1 + y dy[/tex], coming out with 6*pi. My book says this isn't right. Did I do anything wrong? Use the wrong formula?
 
Last edited:

Answers and Replies

  • #2
AKG
Science Advisor
Homework Helper
2,565
3
The enclosed area is not between y=1 and y=3.
 
  • #3
53
0
Oh wait...I think I got it.

I was graphing with the equation set equal to x, when it should have been set equal to y. This would make [tex]\int_{-1}^{3} 1 + y dy[/tex], which, when multiplied by pi, would get 8*pi.

Thanks.
 

Related Threads on Area betweeen curves

Replies
8
Views
2K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
3
Views
951
Replies
1
Views
474
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
5
Views
12K
  • Last Post
Replies
2
Views
954
  • Last Post
Replies
5
Views
934
  • Last Post
Replies
1
Views
924
  • Last Post
Replies
4
Views
1K
Top