Double integration using trig term

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Homework Help Overview

The discussion revolves around a double integral involving the sine function, specifically the integral \(\int^1_0 \int^1_y \sin(x^2) \, dx \, dy\). Participants are exploring methods to evaluate this integral, particularly through changing the order of integration.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss reversing the order of integration as a potential method to simplify the problem. There are questions regarding the correctness of the new limits of integration and the interpretation of the region defined by the original limits.

Discussion Status

The conversation has progressed with some participants suggesting new bounds for the integral and simplifying the expression. There is acknowledgment of a correct approach, though no consensus on the final evaluation has been reached.

Contextual Notes

Participants mention the difficulty of integrating the original expression directly and the importance of visualizing the region defined by the limits to correctly set up the reversed integral.

glog
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Homework Statement



[tex]\int^1_0 \int^1_y sin(x^2) dx dy[/tex]

The Attempt at a Solution



This equation cannot be integrated nicely, so I tried to reverse the order of integration:

[tex]\int^1_0 \int^1_x sin(x^2) dy dx[/tex]

However this only helps for the first step, since when we intregrate by y, we get:

[tex]\int^1_0 sin(x^2)-xsin(x^2) dx[/tex]

I'm stuck... again! Any ideas?
 
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glog said:
This equation cannot be integrated nicely, so I tried to reverse the order of integration:
[tex]\int^1_0 \int^1_x sin(x^2) dy dx[/tex]
Your limits in the new double integral is incorrect. If in doubt, look at the original double integral and draw a picture of the region enclosed by the limits. Then try to express the limits of the double integral in the reversed order of the same region.
 
Alright so perhaps the bounds are then: [tex]\int^1_0 \int^x_0[/tex]

In which case, my integral simplifies to:

[tex]\int^1_0 x sin(x^2)[/tex]

Which becomes:

-1/2 cos (x^2) | 1_0

This make sense?
 
Yep, you got it.
 

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