A mass suspended from a spring is pulled down a distance of 30 cm from its rest position. The mass is

released at time t = 0 and allowed to oscillate. If the mass returns to this position after 2 seconds, find
two different sinusoidal equations that models this motion.

we know that the

amplitude = 30
the period is 4
it has a minimum at t=0
so,
y = -30cos(π/2 t)