Integrating by parts

  • Thread starter AnnieF
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  • #1
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Homework Statement



∫r^3/(4+r^2)^(1/2) dr

Homework Equations



∫udv=uv-∫vdu

The Attempt at a Solution



I know that integration by parts must be used. I tried doing it with 4+r^2 as u, but kept running into issues..then I got an answer but it appears to be wrong. I guess I am not sure how to do this.
 

Answers and Replies

  • #2
ehild
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First substitute r^2=t, then integrate by parts.


ehild
 
  • #3
Dick
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I don't think it needs integration by parts. I'd do a simple u substitution. u=r^2+4, like AnnieF suggested. What 'issues' were you running into?
 
  • #4
I don't think it needs integration by parts. I'd do a simple u substitution. u=r^2+4, like AnnieF suggested. What 'issues' were you running into?
The substitution [itex]u=r^2[/itex] would be significantly easier to deal with. One can then use parts or another substitution to make the integral elementary.
 

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