Concept:
Rolle's theorem says that if \(f\) is continuous on \([a,b]\), differentiable on \((a,b)\), and
\[
f(a)=f(b)
\]
then there exists at least one \(c\in(a,b)\) such that
\[
f'(c)=0
\]
Step 1: Verify endpoint values.
Given,
\[
f(x)=\sin x
\]
on
\[
[0,\pi]
\]
Now,
\[
f(0)=\sin0=0
\]
and
\[
f(\pi)=\sin\pi=0
\]
Thus,
\[
f(0)=f(\pi)
\]
Step 2: Differentiate the function.
\[
f'(x)=\cos x
\]
By Rolle's theorem,
\[
f'(c)=0
\]
So,
\[
\cos c=0
\]
Step 3: Solve in \((0,\pi)\).
In the interval
\[
(0,\pi)
\]
we have
\[
\cos c=0
\]
at
\[
c=\frac{\pi}{2}
\]
Step 4: Final answer.
\[
\boxed{\frac{\pi}{2}}
\]