设f(x)∈C[0,1],证明∫(π,0)*x*f(sinx)dx =π/2*∫(π,0)*f(sinx)dx
问题描述:
设f(x)∈C[0,1],证明∫(π,0)*x*f(sinx)dx =π/2*∫(π,0)*f(sinx)dx
答
设x = π - y,dx = - dy当x = 0,y = π当x = π,y = 0∫(0→π) xf(sinx) dx = - ∫(π→0) (π - y)f(sin(π - y)) dy= π∫(0→π) f(siny) dy - ∫(0→π) yf(siny) dy= π∫(0→π) f(sinx) dx - ∫(0→π) xf(s...