A floating leaf bobs up and down a total of 8 cm. the leaf completes 3 complete cycles in 8 seconds. (Assume equilibrium at t=0.)Write an equation to model the simple harmonic motion.

Can someone explain to me why the answer to this problem is d=4sin(3pi/4)t?

4 is half the max displacement

period = 8/3 seconds, = 2π/k, so k = 3π/4