Answer: Option B
Explanation:
The general cosine function has the following form
Where A is the amplitude: half the vertical distance between the highest peak and the lowest peak of the wave.
is the period: time it takes the wave to complete a cycle.
k is the vertical displacement.
The maximum value of y is is 0.75 and the minimum is -0.75. Then the amplitude A is:
Then

The cycle is repeated every
units
So the period is
Thus:
The function is:
when
y is maximum therefore
As shown in the graph