1. Changes in the depth of water in a small tidal estuary relative to a fixed reference depth can be modelled using the function $y=sin(22.5t)^{\circ}$, where $y$ is measured in metres and t is the time in hours.

(i) Sketch the function for the interval $0\leqt\leq8$.

(ii) If $t=0$ represents 2pm, during what times, to the nearest half hour, will the estuary be at or above the halfway point between $y=0$ and its maximum depth?