Solve Indefinite Integral (x^3)sqrt((x^2)+4)dx

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SUMMARY

The forum discussion focuses on solving the indefinite integral of the function (x^3)sqrt((x^2)+4)dx. The solution involves using the substitution x = 2tan(θ) and dx = 2sec²(θ)dθ, leading to a simplified expression. The final answer is confirmed as (1/5)((x^2)+4)^(5/2) - (4/3)((x^2)+4)^(3/2) + C. A suggestion is made to consider algebraic substitution, specifically u² = x² + 4, before applying trigonometric methods.

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Homework Statement



Indefinite Integral

(x^3)sqrt((x^2)+4)dx


Homework Equations



With an x= 2tan@
and dx= 2 (sec^2)@ d@

The Attempt at a Solution


I get to
8(tan^3)@(sqrt((4tan^2)@+(8sec^2)@d@

Simplified down to

8(tan^3)@(sqrt((12tan^2)@+8d@

After that I'm stuck

The answer is

(1/5)((x^2)+4)^(5/2)-(4/3)((x^2)+4)^(3/2)+C

Thanks very much to the posters on my previous thread
 
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Try an algebraic substitution before you jump into trig, like u^2=x^2+4.
 

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