若f“(x)在[0,π]连续,f(0)=2,f(π)=1,求定积分上线π,下线0[f(x)+f"(x)]sinx dx

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若f“(x)在[0,π]连续,f(0)=2,f(π)=1,求定积分上线π,下线0[f(x)+f

若f“(x)在[0,π]连续,f(0)=2,f(π)=1,求定积分上线π,下线0[f(x)+f"(x)]sinx dx
若f“(x)在[0,π]连续,f(0)=2,f(π)=1,求定积分上线π,下线0[f(x)+f"(x)]sinx dx

若f“(x)在[0,π]连续,f(0)=2,f(π)=1,求定积分上线π,下线0[f(x)+f"(x)]sinx dx
∫(0~π) f(x) sinx dx = ∫(0~π) f(x) d(-cosx)
= - f(x) * cosx |(0~π) + ∫(0~π) cosx df(x)
= - [(f(π) * -1) - (f(0) * cos(0))] + ∫(0~π) cosx * f'(x) dx
= 3 + ∫(0~π) f'(x) d(sinx)
= 3 + f'(x) * sinx |(0~π) - ∫(0~π) sinx df'(x)
= 3 + 0 - ∫(0~π) sinx * f''(x) dx
==> ∫(0~π) f(x) sinx dx = 3 - ∫(0~π) f''(x) * sinx dx
==> ∫(0~π) [f(x) + f''(x)] sinx dx = 3