Solution

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

The first boundary is . On in the first quadrant, the inverse parabolic polar coordinates give . To identify the remaining curve, put . Its Cartesian coordinates satisfy
Hence and , so this boundary is . The condition on this curve requires . Its endpoints are and , while meets at . These three arcs enclose exactly
Every point in this region has , and therefore , as required. Using the Jacobian determinant, the area is

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