what is the period of these functions y=1/2 cos 3pi/2
y=2 cos piX/2
your first equation
y=1/2 cos 3pi/2 has no variable on the right side, so it is simply a straight line y = 0 or the x-axis
for y = 2 cos πx/2
the period = 2π/(π/2)
= π(2/π) = 2
after you find your typo, in the first equation,
take 2π/(coefficient of the angle) to get the period