Integrate r^3√(r^2+1)| Justin's Q&A

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SUMMARY

The integral of the function ∫ r^{3}√(r^{2}+1) dr can be effectively solved using a single u-substitution. By letting u = r^{2} + 1, the differential du = 2r dr simplifies the computation. This approach eliminates the need for trigonometric substitution, making the process more straightforward.

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J Goodrich
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How does one compute

\int r^{3}\:\sqrt{r^{2}+1}\:dr

Does this involve double u sub or trig sub?

Thanks in advance,
Justin
 
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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:)
 
I would think the second was easiest: Let u= r^2+ 1. Then du= 2rdr and r^2= u- 1. (A single u-substitution, not double.)
 

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