设f(x)在[a,b]上连续,且f(b)=a,f(a)=b,证明∫(上b下a)f(x)f'(x)dx=1/2(a²-b²)
问题描述：
设f(x)在[a,b]上连续,且f(b)=a,f(a)=b,证明∫(上b下a)f(x)f'(x)dx=1/2(a²-b²)
答
积分=∫f(x)df(x)=[f(x)]^2/2=[f(b)]^2/2-[f(a)]^2/2=(a^2-b^2)/2