Integrating a non-elementary function

In summary, the conversation is about a double integral that cannot be integrated as is. The person is trying to rearrange the parameters to make it solvable and is seeking verification on their method. They also mention having trouble with the final integration step and ask for help on directly integrating a non-elementary function. Another person suggests treating sin(y^2) as a constant and using a u-substitution to make the integral easier to solve.
  • #1
bosox09
7
0

Homework Statement



Integral (pi1/2, 0) of Integral (pi1/2, y) sin(y2) dxdy

Homework Equations



This one is interesting because it can't be integrated as is (at least not at the level of my course) but I think with some rearranging it can be done. I was wondering if anyone could verify my method.

BTW, I'm kinda new, so I don't know exactly how to make the little integral symbol. If that's too hard to read, it's a double integral defined on the inside between "y" and the square root of pi, and defined on the outside between 0 and the square root of pi. The function is sin(y2), with dx, then dy. That is, I believe 0 < y < pi1/2 and y < x < pi1/2.

The Attempt at a Solution



Alright so as is, it's not an elementary function and cannot be worked with, I believe. I rearranged the "parameters" to define x as 0 < x < pi1/2 and 0 < y < x. Then, "dx" and "dy" switch positions in the original equation, and I integrated sin(y2) with respect to "x" first. Simply put, I got xsin(y2). Then, integrating with respect to "y" by parts, I got xsin(y2) - [(1/2)(x2) * -(2y)(cos(y2))]. Without doing all the math here, I'll tell you I ended up with pi2.

I feel I got the problem right all the way until the final integration. I'm mostly afraid I messed up the final step in integration. If anyone would like to look at my process, that would be great.

PS -- if anyone knows how to directly integrate a non-elementary function, that would be cool to see.
 
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  • #2
Is your integral:


[tex]\int_{0}^{\sqrt\pi}\int_{y}^{\sqrt\pi}sin(y^2)dxdy[/tex]


?

If this is the integral you are working with then, notice that you are first integrating with respect to x, so you can treat

[tex]sin(y^2)[/tex] merely as a constant. And after you have integrated with respect to x, you will end up with an integral that can be easily integrated with a u-substitution.
 
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  • #3
Sorry! Good point.

The integral I put was not the original. I rearranged the original to get to that point, so ignore my "process" as that's how I got to the formula above. Thanks.
 

FAQ: Integrating a non-elementary function

What is the definition of a non-elementary function?

A non-elementary function is a mathematical function that cannot be expressed in terms of elementary functions such as polynomials, exponentials, logarithms, and trigonometric functions. These functions often involve complex operations or infinite series.

Why is integrating a non-elementary function challenging?

Integrating a non-elementary function is challenging because it requires advanced mathematical techniques such as substitutions, integration by parts, or series expansions. These techniques can be complex and time-consuming, and there is no one-size-fits-all approach to solving these integrals.

Can a non-elementary function be integrated analytically?

Yes, some non-elementary functions can be integrated analytically, but it depends on the specific function. Some functions may have a known closed-form solution, while others may require approximations or numerical methods to evaluate the integral.

What are some common techniques for integrating non-elementary functions?

Some common techniques for integrating non-elementary functions include integration by parts, substitution, partial fractions, and series expansions. These techniques often involve manipulating the integral to transform it into a form that can be evaluated using known integration rules.

How can I check if my integration of a non-elementary function is correct?

You can check if your integration of a non-elementary function is correct by taking the derivative of the result and comparing it to the original function. If the two functions are equal, then your integration is correct. Additionally, you can use software or online tools to verify your result or compare it to known solutions.

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