Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2015/paper-2/9/solution

The original PDF contains the product ; the transcription drops the after the first sine. Using gives the finite Fourier sine series
Thus , , and all other sine coefficients vanish. No cosine or constant terms are present.

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