a) Recall that:
[tex]-1\le\cos \theta\le1.[/tex]
Therefore:
[tex]\begin{gathered} -1\le\cos (30^{\circ}\times t)\le1, \\ -12\le12\cos (30^{\circ}\times t)\le12, \\ -12+16\le12\cos (30^{\circ}\times t)+16\le12+16, \\ 4\le12\cos (30^{\circ}\times t)+16\le28. \end{gathered}[/tex]
Therefore the minimum height of the Ferris wheel above the ground is 4 meters.
b) Recall that to evaluate a function at a given value, we substitute the variable by the given value, then, evaluating the given function at t=3 we get:
[tex]12\cos (30^{\circ}\times3)+16.[/tex]
Simplifying the above result we get:
[tex]\begin{gathered} 12\cos (90^{\circ})+16, \\ 12\cdot0+16, \\ 0+16, \\ 16. \end{gathered}[/tex]
Therefore, the height of the Ferris wheel above the ground after 3 minutes is 16 meters.
(c) Let x be the time in minutes the Ferris wheel takes to complete one full rotation, then we can set the following equation:
[tex]30^{\circ}\times x=360^{\circ}.[/tex]
Therefore:
[tex]30x=360.[/tex]
Dividing the above equation by 30 we get:
[tex]\begin{gathered} \frac{30x}{30}=\frac{360}{30}, \\ x=12. \end{gathered}[/tex]
Answer:
(a) 4 meters.
(b) 16 meters.
(c) 12 minutes.
