Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2023/iii/paper-115/1/c/solution

Choose a coordinate ball around and a smaller convex coordinate ball whose closure lies in . For , let be the constant coordinate vector from to . Choose a smooth bump function supported in and equal to one on , and define in the chart
extending it by zero outside . This is a compactly supported smooth vector field. The segment stays in , where , so uniqueness for ordinary differential equations gives
In particular, .

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