# Math Help - show the equality

1. ## show the equality

Let f be a function such that f' is continuous on [a,b]. show that

$\int _a\,^b\!f(t)f'(t)dt$ = $1/2[f^2(b) - f^2(a)]$

2. Originally Posted by wopashui
Let f be a function such that f' is continuous on [a,b]. show that

$\int _a^{\,b}\!f(t)f'(t)dt$ = $1/2[f^2(b) - f^2(a)]$
Substitute $u=f(t)$.