trig
posted by Kayla .
Write an equation for simple harmonic motion, given that the amplitude equals 4 inches and the period equals 2 seconds and the max displacement occurs when t=0. answers: y=4sin pi t, y=4cos pi t, y=4cos t, y=4sin2 pi t

when t=0 , all answers with sin are zero
all answers with cosine are 4, so we eliminate the sine answers
period of a sine or cosine function is 2π/k
but we are told:
2π/k = 2
k = π
so it must be y = 4cos πt