Hi,

a particle is moving in simple harmonic motion such that a = -4x. ( x in metres, t in seconds)

Find the maximum speed at which the particle is travelling.

Velocity = 6cos2t.

My teacher said to put t = 0 and sub it into velocity equation above, but I don't know why?
Thanks!

the cosine function varies between -1 and 1, so the maximum value of cosine is 1.

That occurs at t=0, (and every multiple time). So Velocity= 6*cos2*0)=6