Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-oxford/2017/prelims/mathematics-v-resit/question-5/c/solution

Here and , so D'Alembert's formula gives
Only the overlap with the support of the initial velocity contributes. Therefore
The relevant interval is determined by the two characteristic lines for the one-dimensional wave equation through the observation point.

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