Here's the question you clicked on:
MissKhan
if f(x)=sin(x) for all x, then average value of f on the interval (0,pi) is ?
\[ \overline{f}=\frac{1}{b-a}\int_a^bf(x)\;dx \]
\(a=0,\;b=\pi,\;f(x)=\sin(x)\)
we have the answer 2/pi ?
http://www.wolframalpha.com/input/?i=average+sin+x++x+%3D+0+to+pi