Sketch the graph of the function $y=2\cos x$. Label all the $x-$intercepts on your sketch graphs.

After you exercise, the velocity of air flow(in $\mathrm{litres}$ per $\mathrm{second}$) into your lungs can be modelled by the equation $y=2\sin \left(90°t\right)$.

Draw the graph of the function in the first $8 \mathrm{seconds}$.

When you ride a Ferris wheel, your vertical height above the ground changes. The relationship between your height above the ground and the time for a complete revolution of the wheel can be modelled with the sinusoidal graph given below. Find a function that models the graph.

The height in meters of the tide above the mean sea level on one day at Bal Harbour can be modelled by the function $h\left(t\right)=3\sin 30°t$, where $t$ is the number of hours after midnight. A ship can cross the harbour if the tide is at least $2 \mathrm{m}$ above the average sea level. Determine the time when it can cross the harbour.

For the following graph, find the amplitude, frequency, and period. Then, write down the equation that represents the function.