# Math Help - Polar Integral Setup

1. ## Polar Integral Setup

Evaluate the given integral by changing to polar coordinates. double integral xdA (not sure how to insert double integral symbols)
, where D is the region in the first quadrant that lies between the circles x^2 + y^2 = 4 and x^2 + y^2 = 2x

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No need to do it, just help me with setting this up as i always run into problems with this. Thanks.

2. Originally Posted by purplerain
Evaluate the given integral by changing to polar coordinates. double integral xdA (not sure how to insert double integral symbols)
, where D is the region in the first quadrant that lies between the circles x^2 + y^2 = 4 and x^2 + y^2 = 2x

===========================

No need to do it, just help me with setting this up as i always run into problems with this. Thanks.
Use completing the square to get the 2nd equation into a workable format!

$x^2 + y^2 - 2x = 0$

$(x-1)^2 +y^2 - 1 = 0$

$(x-1)^2 + y^2 = 1$

So now you have a circle centred at the origin with a radius of two, given by the first equation, and a circle centred at the point (1,0) with a radius of 1. Draw these, and see if the image makes it easier you to visualise the integral.

Although I'm not sure what they mean by the 'area that lies between the circles', because there is no area BETWEEN them... one circle is inside the other.