Change to polars double integral

In summary, the conversation is about converting to polar coordinates and determining the ranges in terms of r and θ. The question asked for help in converting the ranges and the solution involved sketching the region of integration and finding the ranges from there.
  • #1
Kuma
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Homework Statement



Here is the question

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Homework Equations


The Attempt at a Solution



So converting to polars by x = r cos θ, y = r sin θ gives me r^5 in the inner integral

but how do you convert the ranges?

y goes from 0 to sqrt 1 - x^2, so that is just r, I could tell just by looking at it, but in a harder question how do you derive the range in terms of r? x goes from 0 to 1, but how do you convert that in terms of θ (an angle)?
 
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  • #2
Have you sketched the region of integration?
 
  • #3
Draw the domain of integration in the x,y plane (like in the figure) and find the ranges of θ and r from there.

ehild
 

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1) What is the purpose of using polar coordinates in a double integral?

The use of polar coordinates in a double integral allows for the evaluation of integrals over non-rectangular regions, which can often simplify calculations and make them more efficient.

2) How do you convert from rectangular coordinates to polar coordinates?

To convert from rectangular coordinates (x,y) to polar coordinates (r,θ), you can use the equations r = √(x^2 + y^2) and θ = tan^-1(y/x).

3) What is the difference between a single integral and a double integral in polar coordinates?

A single integral in polar coordinates is used to find the area under a curve, while a double integral is used to find the volume under a surface. In polar coordinates, a double integral is written as ∫∫f(r,θ)rdrdθ, where f(r,θ) is the function being integrated over the region.

4) Can you explain the concept of "change of variables" in a double integral using polar coordinates?

In a double integral, "change of variables" refers to the substitution of polar coordinates for rectangular coordinates in the integrand. This allows for a simplification of the integral and makes it easier to evaluate.

5) How does the region of integration change when using polar coordinates in a double integral?

In polar coordinates, the region of integration is typically a circular or semi-circular shape, rather than a rectangular shape as in rectangular coordinates. This can make the bounds of integration and calculation of the integral more straightforward.

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