Ivan Shishkin, Rye (1878)

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Solution

Solution by Sequoia · EN

The function f ⁣:xx8sin(x)f\colon x\longmapsto x^8\sin(x) is odd since xsin(x)x\longmapsto\sin(x) is odd and xx8x\longmapsto x^8 is even.
Hence:
I:=ππf(x)dx=u=xππf(u)(du)=ππ(f(u))du=II:=\int_{-\pi}^{\pi}f(x)\,\mathrm{d}x\overset{u=-x}{= }\int_{\pi}^{-\pi}f(-u)\,(-\mathrm{d}u)=\int_{-\pi}^{\pi}(-f(u))\,\mathrm{d}u=-ISo I=0I=0.

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