Non-elementary Integral: Solving x^2sin(x)/(1+x^6) using Substitution Method

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Homework Help Overview

The discussion revolves around solving the integral of x²sin(x) / (1+x⁶) from -π/2 to π/2, with a focus on the substitution method. Participants explore the nature of the integral and its potential classification as a non-elementary integral.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts various substitutions for u, including u = x², u = 1+x⁶, and u = sin(x), but finds that none effectively simplify the integral. They question the feasibility of solving it with substitution and express a desire to avoid methods like Taylor series.

Discussion Status

Some participants note that the function is odd over the specified interval, suggesting that this characteristic may influence the integral's evaluation. Others reference previous experiences with similar integrals, indicating that the results often involve complex functions like sine and cosine integrals. There is a recognition of the integral's complexity, with some suggesting computational tools for verification.

Contextual Notes

Participants discuss the implications of the function being odd and its symmetry over the interval, which may lead to a conclusion about the integral's value. The original poster also mentions constraints regarding the use of certain methods, such as Taylor series.

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Homework Statement



Solve the integral of x2sin(x) / (1+x6) from -pi/2 to pi/2.

Homework Equations



none

The Attempt at a Solution



Well I am supposed to do this using the substitution method, so I tried:

u = x2
du = 2x dx which doesn't cancel out any terms

u = 1+x6
du = 6x5 dx which again doesn't cancel anything out

u = sin(x)
du = cox(x) dx useless also

Is this possible with substitution? I seem to have tried every option for u. Is there another way to do this? (without taylor series and stuff like that)

Thanks for the help!Also, I tried doing this integral on the computer, and it said it cannot be solved because it is probably a "non-elementary integral", hence the title of the thread.
 
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The function is odd on that interval. f(-x)=-f(x).
 
Last edited:
I had a similar question earlier. The result is a whole bunch of sine and cosine integrals and imaginary parts. I don't understand how one would do this, but go ahead and put it in the integrator (mathematica) and check the answer out. What level is this for?
 
For a symmetric function that is odd, the integral on the interval -a to a = 0 !
Thanks guys.
 

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