Find the integral x^3 sqrt(x^2 + x^8 + 8) cos x dx

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    Cos Dx Integral
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Homework Help Overview

The discussion revolves around finding the integral of the function f(x) = x^3 sqrt(x^2 + x^8 + 8) cos(x) dx, with a specific focus on evaluating it over the interval from -14 to 14.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss potential methods for starting the integration, including integration by parts and substitution. There is also a question regarding whether the integral is definite and how that might affect the approach.

Discussion Status

Some participants have noted that the function is odd and have pointed out the implications of integrating an odd function over a symmetric interval. This has led to a discussion about the cancellation of positive and negative areas under the curve.

Contextual Notes

There is a focus on the nature of the function being odd and its evaluation over a symmetric interval, which may influence the outcome of the integral.

golb0016
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Homework Statement


Find the integral

f(x) = x^3 sqrt(x^2 + x^8 + 8) cox(x) dx


The Attempt at a Solution



I need help starting. It appears to be either integration by parts and/or substituion.
 
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You are going to have a tough time finding an antiderivative for that. Is it actually a definite integral?
 


The problem wanted the function evaluated from -14 to 14. Does it make a difference if it is definitive or not? Is there a trick if it is definitive?
 


golb0016 said:
The problem wanted the function evaluated from -14 to 14. Does it make a difference if it is definitive or not? Is there a trick if it is definitive?

It does in this case. For your function f(-x)=(-f(x)), it's an odd function. What happens if you integrate an odd function over a symmetric interval around the origin?
 


Does the positive and negative parts cancel out if it is symmetric?
 


golb0016 said:
Does the positive and negative parts cancel out if it is symmetric?

That's the idea.
 

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