posted by jerson .
for the graph of y=-5sin x/2, state frequency
for y = a sin kx
the period is 2pi/k
so isn't your equation y = -5sin(1/2)x ?
for k = 1/2
can you take it from there?
no, the frequency is 1/2, namely the k value of
y = a sin kx.
for yours, the "period" is 2pi/(1/2) = 4pi
which means it takes 4pi radians on your graph to complete one complete sine curve.
by frequency we want the number of cycles of the sine or cosine curve we would get from 0 to 2pi, which would be 1/2 or the k value of the sin kx .