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Improper double integrals

asked 2014-07-21 10:17:19 -0600

Anonymous gravatar image

In section 15.2, question #19a, it asks: Consider the integral $\int\int 1/\sqrt{x^2+y^2} dA$, where $D$ is the unit disk centered at the origin. a) Why might this integral be considered improper?

The link to see this graph did not work for me, but I used wolfram alpha and the graph looked kind of like a piece of paper being folded upwards. I don't know why this could be considered improper? Any thoughts?

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answered 2014-07-21 11:01:34 -0600

SpaceManSpiff gravatar image

To talk about this we need to remember what makes an integral improper.

An integral is improper when it is bound by an asymptote or infinity.

When $x$ and $y$ are equal to zero in this function the function will be undefined and $z$ values will become arbitrarily large as $x$ and $y$ approach zero. So your integral bounds for the $dr$ part of the problem will be at an asymptote.

This makes the integral improper.

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Asked: 2014-07-21 10:17:19 -0600

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Last updated: Jul 21 '14