Ferris Wheel Park
1. **Problem 1: Write an equation for the height $h$ of a point on the Ferris wheel as a function of time $t$.**
Given:
- Maximum height $= 17$ m
- Minimum height $= 1$ m
- The function form: $h = a \cos[b(t - c)] + d$
2. **Step 1: Find amplitude $a$ and vertical shift $d$.**
- Amplitude $a = \frac{\text{max} - \text{min}}{2} = \frac{17 - 1}{2} = 8$
- Vertical shift $d = \frac{\text{max} + \text{min}}{2} = \frac{17 + 1}{2} = 9$
3. **Step 2: Find period and calculate $b$.**
- The graph completes 2 full cycles in 60 seconds, so period $T = \frac{60}{2} = 30$ seconds
- Formula for $b$: $b = \frac{2\pi}{T} = \frac{2\pi}{30} = \frac{\pi}{15}$
4. **Step 3: Use given phase shift $c$.**
- Given in the problem: $c = 13$
5. **Step 4: Write the equation.**
$$h = 8 \cos\left[\frac{\pi}{15}(t - 13)\right] + 9$$
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6. **Problem 2: Find values of $b$ and $d$ for Ellie's distance function $s(t) = a \cos[b(t - c)] + d$.**
Given:
- Radius of park $= 195$ m
- Shortest distance from running trail to parking lot $= 5$ m
- Ellie completes 4 laps in 32 minutes
7. **Step 1: Calculate $d$ (vertical shift).**
- The distance $d$ is the centerline of the cosine function, which is the radius plus the shortest distance to the parking lot:
$$d = 195 + 5 = 200$$
8. **Step 2: Calculate period and $b$.**
- Time for one lap $= \frac{32}{4} = 8$ minutes
- Period $T = 8$
- Calculate $b$:
$$b = \frac{2\pi}{T} = \frac{2\pi}{8} = \frac{\pi}{4}$$
9. **Step 3: Match $b$ and $d$ to the options.**
- $b = \frac{\pi}{4}$ and $d = 200$
- This corresponds to option D.
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**Final answers:**
1. Ferris wheel height function:
$$h = 8 \cos\left[\frac{\pi}{15}(t - 13)\right] + 9$$
2. Values for Ellie's distance function:
$$b = \frac{\pi}{4}, \quad d = 200$$
Option D is correct.