Double Integral - Polar Coordinates

duki
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Homework Statement



Evaluate by changing to polar coordinates

Homework Equations



Can't figure out how to make the integral stop after the sqrt(9-x^2)
\int_0^\frac{3}{\sqrt(2)} \int_x^{\sqrt(9-x^2)} e^-(x^2+y^2) dy dx

The Attempt at a Solution



I'm not sure where to really start on this one. I know it will end up being e^-r^2 but beyond that I'm not sure.
 
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You'll have to express dxdy in other variables, and the intervals have to be changed.
 
How can I change them to polar coordinates?
 
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First of all: Draw a figure in the xy-plane with to see what shape the domain yields (probably something like a circle sector). Then you should be able to figure out what values you should give r and \phi. You usually substitute r*drd\phi for dxdy when using polar coordinates. However, the exact expression depends on what shape the domain yields.
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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