Sea sick tyring to figure this out

Question

Coastal areas experience tides which is where the ocean periodically gets to high and low points. Tides can be modeled with a sinusoidal (sine or cosine) function. At one beach, the high tide is 6 feet above mean sea level and the low tide is 6 feet below see level. The length of time between high and low tide is 7 hours.

If high tide is at time t=0t=0 hours, give the function H(t) that describes the height of the tide relative to sea level tt hours after the high tide.

Answer 1

l(t)=6cos(2πt/14)

check, t=0, l(t)=6

t=7, l(t)= -6

Answer 2