Double integration using trig term

In summary, the original given double integral cannot be integrated nicely and the attempt to reverse the order of integration only helps with the first step. However, by correctly setting the limits in the new double integral, the integral simplifies to -1/2 cos(x^2) from 0 to 1.
  • #1
glog
17
0

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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  • #2
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.
 
  • #3
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?
 
  • #4
Yep, you got it.
 

1. What is double integration using trig term?

Double integration using trig term is a method of finding the area between two curves by integrating the difference between the two curves. This involves using trigonometric functions, such as sine and cosine, to express the curves in terms of an angle.

2. When is double integration using trig term used?

Double integration using trig term is often used in calculus and engineering to find the area of irregular shapes or to solve problems involving periodic motion, such as pendulums or springs.

3. How is double integration using trig term performed?

To perform double integration using trig term, you must first express the curves in terms of an angle using trigonometric functions. Then, you integrate the difference between the two curves with respect to that angle. Finally, you use the limits of integration to find the area between the two curves.

4. What are the benefits of using double integration using trig term?

Double integration using trig term allows for the calculation of more complex areas that cannot be easily solved using basic integration methods. It also allows for the analysis of periodic motion and other problems involving trigonometric functions.

5. What are some common mistakes when using double integration using trig term?

Some common mistakes when using double integration using trig term include forgetting to express the curves in terms of an angle or using the wrong limits of integration. It is also important to check for symmetry and use the correct trigonometric identities when integrating.

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