Double Integral - polar coordinates

And your integration steps look correct. To integrate the third root term, you can use the substitution u = 4 - r^2. Then the integral becomes \int \sqrt{u} du, which can be simplified using the power rule. Overall, your solution looks correct. In summary, the given double integral can be rewritten in polar coordinates and solved by integrating from 0 to 2 for the radius and from 0 to π for the angle. Using the substitution u = 4 - r^2, the third root term can be integrated using the power rule.
  • #1
exidez
44
0

Homework Statement



[tex]
\displaystyle\int\int\sqrt{4-x^2-y^2} dA
[/tex]

[tex]
R{(x,y)|x^2+y^2\leq4 .. 0\leq x}
[/tex]

The Attempt at a Solution



So far i have: [tex]
\displaystyle\int^{\pi}_{0}\int^{r}_{0}\sqrt{4-r^2} rdrd\theta
[/tex]

Solving i get:
[tex]
\displaystyle\int^{\pi}_{0}\frac{-1}{3}(4-r^2)^{\frac{3}{2}}+\frac{1}{3}(4)^{\frac{3}{2}}d\theta
[/tex]

Am i on the right track, and if so how do i integrate the third root term?edit//

ok i forgot the radius goes from 0 to 2... if i sub 2 into r, i can integrate it. But just to check, am i still doing this correctly?
 
Last edited:
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  • #2
exidez said:
edit//

ok i forgot the radius goes from 0 to 2... if i sub 2 into r, i can integrate it. But just to check, am i still doing this correctly?

Yes, you should integrate from zero to 2.
 

FAQ: Double Integral - polar coordinates

1. What is a double integral in polar coordinates?

A double integral in polar coordinates is a mathematical tool used to calculate the area of a two-dimensional region bounded by a polar curve. It involves integrating a function over a region represented by polar coordinates (r, θ).

2. How do you convert a double integral from Cartesian coordinates to polar coordinates?

To convert a double integral from Cartesian coordinates (x, y) to polar coordinates (r, θ), you can use the following formula:
∫∫f(x,y)dA = ∫∫f(rcosθ, rsinθ)rdrdθ

3. What is the significance of the Jacobian in double integrals in polar coordinates?

The Jacobian in double integrals in polar coordinates is a scaling factor that accounts for the change in variables from Cartesian to polar coordinates. It is represented by the determinant of the transformation matrix and is necessary to correctly calculate the integral in polar coordinates.

4. What are some applications of double integrals in polar coordinates?

Double integrals in polar coordinates are commonly used in physics and engineering to calculate the mass, center of mass, and moments of inertia of objects with circular or symmetric shapes. They are also used in calculating electric and gravitational fields, and in solving problems involving polar coordinates in real-life scenarios.

5. Is it possible to use a double integral in polar coordinates to evaluate a triple integral?

Yes, it is possible to use a double integral in polar coordinates to evaluate a triple integral in some cases. This can be done by first converting the triple integral to cylindrical coordinates and then using the double integral formula in polar coordinates. However, this method may not be applicable in all cases and may require additional transformations.

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