Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-oxford/2017/prelims/mathematics-v-resit/question-1/c/solution

The inequalities become the rectangle , in parabolic polar coordinates. The change of variables formula and the Jacobian determinant from a give the area
The middle panel in b shows the curved region in Cartesian coordinates; its straight edges in parabolic polar coordinates explain the simple integration limits.

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