How to i differentiate 8 sin pit/4?

Question

so the answer is wrong as it is 32/pi cos (pit/4)

Answer 1

f(t) = y = 8 sin (π t / 4)
Let u = πt / 4
du / dt = π / 4
y = 8 sin u
dy/du = 8 cos u
dy/dt = (du/dt).(dy/du)
dy/dt = (π/4).(8 cos u)
dy/dt = (π/4).(8).cos (πt / 4)
dy/dt = (2π).cos (πt / 4)

Answer 2

y = 8 sin pi t/4

dy/dx = -8(cos pi t/4)*(pi/4)

dy/dx = -2pi(cos pi t/4)

Answer 3

d(sin) = (-cos)(dx)

d(8 sin pit/4) = -8cos(pit/4)*(pi/4)
= -2pi(cos(pit/4))