trig
posted by ske .
The average depth of water at the end of a dock is 6 ft. This varies 2 ft in both directions with the ride. Suppose there is a high tide at 4 am. If the tide goes from low to high every 6 hours, write a cosine function describing the depth of the water as a function of time with t=4 corresponding to 4AM.
My work:
y=2cos((pi/6(xd))+6
Ok all I need help is with finding the phase shift. I am having trouble with finding it. Please be detailed. Thanks in advance

take a look at the reply to a student having a question very similar to yours.
http://www.jiskha.com/display.cgi?id=1241479278