Shell method versus disk method

  • Thread starter fiziksfun
  • Start date
  • #1
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I'm confused when to use the shell method vs. the disk method

Specifically in this problem:

If the region encolsed by the y-axis, the line y=2 and the curve y=[tex]\sqrt{x}[/tex] is revolved around the y-axis, the volume of the solid generated is:

However when I use the shell method and the disk method I get different answers

Can someone tell me what I'm doing wrong?

Disk Method:
[tex]\pi[/tex] [tex]\int[/tex]y^4 dy evaluated from 0 to 2

Shell Method:

2[tex]\pi[/tex][tex]\int[/tex]x(2-[tex]\sqrt{x}[/tex])dx

Help please!!
 

Answers and Replies

  • #2
Vid
401
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I got the same answer. Remember the second integral is from 0 to 4 not 0 to 2.
 

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