First we make the composition of functions: f (x) = sin x g (x) = cos x f (g (x)) = sin (cos x) We now evaluate the composite function in pi / 2: f (g (pi / 2)) = sin (cos (pi / 2)) f (g (pi / 2)) = sin (0) f (g (pi / 2)) = 0 Answer: f (g (pi / 2)) = 0