A weight is attached to a spring and is pulled down 7 inches below the equilibrium position. Assuming the period of the system is 1/2 second, determine the trigonometric model that gives the position ( y ) of the weight at time ( t ) second.
a. ( y = 7 sin(4π t) )
b. ( y = 7 sin(2π t) )
c. ( y = 7 cos(4π t) )
d. ( y = 7 cos(2π t) )