Double Integral Over a Region: Finding Limits of Integration

In summary, the conversation discusses the process of finding the limits of integration for the double integral \iint\limits_D x{\rm{d}}x{\rm{d}}y, where x = \sqrt{2y - y^2} and y = \sqrt{2x - x^2}. The process involves determining the bounds for both x and y and then setting up the integral accordingly. It is also mentioned that the integral can be evaluated using polar coordinates as an alternative method.
  • #1
nuuskur
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Homework Statement


[itex]\iint\limits_D x{\rm{d}}x{\rm{d}}y[/itex] where [itex]x = \sqrt{2y - y^2}, y = \sqrt{2x - x^2}[/itex]

Homework Equations

The Attempt at a Solution


I have figured out the region in question:
jlC2Xbj.png
But how do I get the limits of integration?

Ah, perhaps..
[tex]\int_0^1 \int_{1-\sqrt{1-y^2}}^{\sqrt{2y-y^2}} x {\rm{d}}x{\rm{d}}y[/tex]
In the inner integral I consider what X is bound by and then the 2nd integration would be just from 0 to 1 since that's what y is bound by. Not really worried about the actual calculation itself, but the most challenging bit is figuring out the bounds.
 

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  • #2
yep. those bounds look good. I get the same ones at least :)

edit: you could also do the integration in the opposite order (i.e. dy first), but I think that way is more time-consuming. and of course, in that method, the limits would look similar, but would have x instead of y.
 
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  • #3
@nuuskur: Of course, if you were "worried" about evaluating the integral, it would be wise to convert the equations to polar coordinates and set it up and work it that way.
 

1. What is a double integral over a region?

A double integral over a region is a mathematical concept that allows us to calculate the volume under a surface in a three-dimensional space. It involves integrating a function over a region in a two-dimensional plane.

2. How is a double integral over a region different from a regular integral?

A double integral over a region is different from a regular integral in that it involves integrating a function over a two-dimensional region instead of a one-dimensional interval. This means that instead of finding the area under a curve, we are finding the volume under a surface.

3. What is the purpose of calculating a double integral over a region?

The purpose of calculating a double integral over a region is to find the volume under a three-dimensional surface or to solve problems involving two variables, such as finding the center of mass or calculating the average value of a function over a region.

4. How do you evaluate a double integral over a region?

To evaluate a double integral over a region, you first need to determine the limits of integration, which define the boundaries of the region. Then, you can use various integration techniques, such as the Fubini's theorem or the substitution method, to solve the integral.

5. What are some real-world applications of double integrals over a region?

Double integrals over a region have many applications, such as calculating the volume of a solid object, finding the mass and center of mass of an object, calculating the work done by a force on an object, and determining the average value of a function over a region. They are also used in physics, engineering, and economics to model and solve various problems involving multiple variables.

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