Tuesday, 15 July 2014

calculus - Evaluate the double integral by changing to polar coordinates for x2+y2leq4


Change the double integral where D = \{(x,y):x^2+y^2\leq4,y\geq0\} by changing to polar coordinates r, \phi





So am I right in thinking the limits would be 0 and 4 for x and y?



Converting the integral would be



\begin{align} & \int_0^4 \int_0^4 \sqrt{4-x^2-y^2} \, dx \, dy = \iint_D \sqrt{4-r^2\cos^2\phi-r^2\sin^2\phi} \ |r| \, dx \, dy \\[10pt] = {} & \iint_D \sqrt{4-r^2} \, |r| \, dx \, dy \end{align}




I am unsure how to change the coordinates?

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