A bit of fun homework as always.. tides

:) :confused: hi all, just need a bit of guidence with the following.. i don't know where to begin..

so if any1 can help i would really appreciate it!!

1. **Entering the harbour**

The depth y in metres above a horizontal mark on a harbour wall is given by

y=3sin(pi/12)

?

where t? is the time in hours after midday on Monday.

(a) Plot the graph of y=3sin(pi/12) ? for ? 0_< t _< 36.

Hope you cn understand the notation.. this one mean 0 is equal or less than t etc..

(b) The rate of change of depth of water in the harbour is given by dy/dt ? Find dy/dt ? and calculate the rate of change of depth of water when t=19?

(c) List the coordinates of all the stationary points on the graph.

(d) A luxury liner can only enter the harbour when the depth of water is at least 1.5 metres above the horizontal mark. At what times during the week can the liner enter the harbour?

ps. ignore those question marks...not sure what they are there for????