The period of a simple pendulum is 2 seconds, and the amplitude of vibration is 5 cm. Write down the equation for displacement as a function of time:
a) y(t) = 5cos(πt)
b) y(t) = 5sin(πt)
c) y(t) = 5cos(2πt)
d) y(t) = 5sin(2πt)