Integration Problem

  • Thread starter J Goodrich
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  • #1
J Goodrich
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How does one compute

[tex]\int r^{3}\:\sqrt{r^{2}+1}\:dr[/tex]

Does this involve double u sub or trig sub?

Thanks in advance,
Justin
 

Answers and Replies

  • #2
tiny-tim
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Hi Justin! :smile:

(have a square-root: √ and an integral : ∫ and try using the X2 tag just above the Reply box :wink:)

trig sub is probably easiest.

(alternative hint: write it ∫ r(r2)(r2 + 1)1/2 dr :wink:)
 
  • #3
HallsofIvy
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I would think the second was easiest: Let [itex]u= r^2+ 1[/itex]. Then du= 2rdr and [itex]r^2= u- 1[/itex]. (A single u-substitution, not double.)
 

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