Answer:

Explanation:
We start from the general form of the sine function which is:

where
Amplitude= IaI=
=4( which is the maximum value we have above the 0 axis)
Period=

Period=12 (space between high tides)
Isolating b:

Horizontal shift = c (Normally the function starts at 0 but in the excercise we have at midnight hight tide this meaning the function is at its maximum value so we need to move it a quarter of the period so it will have maximum value at t=0)
then
