Just remember these:
y = sin [
f(x) ]
y' =
f'(x) x cos [
f(x) ]
y = cos [ f(x) ]
y' = f'(x) x -sin [ f(x) ]
y = tan [ f(x) ]
y' = f'(x) x sec^2 [ f(x) ]
Let's apply this to the question above:
y = sin [
1/4x + pi/2 ]
So f(x) =
1/4x + pi/2
f'(x) =
1/4
Therefore y' =
1/4 x cos [
1/4x + pi/2 ]
But the question is asking for y'(pi)
So in place of x, we now substitute x = pi
Doing this we get y'(pi) = 1/4 x cos [ 1/4(pi) + pi/2 ] = ________
You can take it step by step until you reach your answer, don't get overwhelmed