High tides occur approximately 12.5 hours apart. Suppose that a harbor is 50 feet deep at high tide and 30 feet deep at low tide. Find a function that models the water depth t hours after high tide. [t = 0 is a high tide]

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
Question
**Problem 2: Modeling Tides in a Harbor**

High tides occur approximately 12.5 hours apart. Suppose that a harbor is 50 feet deep at high tide and 30 feet deep at low tide. Find a function that models the water depth \( t \) hours after high tide. [ \( t = 0 \) is a high tide]

**Explanation:**

To model the water depth in terms of time \( t \), we can use a sinusoidal function because the tides follow a consistent, wave-like pattern. The following steps outline how to derive this function:

1. **Amplitude:** The amplitude is half the difference between the high tide and low tide depths. 
   \[
   \text{Amplitude} = \frac{50 - 30}{2} = 10 \text{ feet}
   \]

2. **Midline:** The midline is the average of the high and low tide depths.
   \[
   \text{Midline} = \frac{50 + 30}{2} = 40 \text{ feet}
   \]

3. **Period:** The period of the function is 12.5 hours because high tides occur every 12.5 hours.
   \[
   \text{Period} = 12.5 \text{ hours}
   \]

4. **Frequency:** The frequency is the reciprocal of the period.
   \[
   \text{Frequency} = \frac{1}{12.5}
   \]

5. **Function:** A cosine function is often used for modeling tides, as it starts from the maximum value at \( t = 0 \). The function can be written as:
   \[
   D(t) = 40 + 10 \cos\left(\frac{2\pi}{12.5}t\right)
   \]

Where:
- \( D(t) \) represents the depth of the water \( t \) hours after high tide.
- \( 40 \) is the midline, representing the average depth.
- \( 10 \) is the amplitude.
- \( \cos\left(\frac{2\pi}{12.5}t\right) \) represents the cosine wave over the period of 12.5 hours.

This function provides a mathematical model for predicting the harbor's water depth at any given time after high tide.
Transcribed Image Text:**Problem 2: Modeling Tides in a Harbor** High tides occur approximately 12.5 hours apart. Suppose that a harbor is 50 feet deep at high tide and 30 feet deep at low tide. Find a function that models the water depth \( t \) hours after high tide. [ \( t = 0 \) is a high tide] **Explanation:** To model the water depth in terms of time \( t \), we can use a sinusoidal function because the tides follow a consistent, wave-like pattern. The following steps outline how to derive this function: 1. **Amplitude:** The amplitude is half the difference between the high tide and low tide depths. \[ \text{Amplitude} = \frac{50 - 30}{2} = 10 \text{ feet} \] 2. **Midline:** The midline is the average of the high and low tide depths. \[ \text{Midline} = \frac{50 + 30}{2} = 40 \text{ feet} \] 3. **Period:** The period of the function is 12.5 hours because high tides occur every 12.5 hours. \[ \text{Period} = 12.5 \text{ hours} \] 4. **Frequency:** The frequency is the reciprocal of the period. \[ \text{Frequency} = \frac{1}{12.5} \] 5. **Function:** A cosine function is often used for modeling tides, as it starts from the maximum value at \( t = 0 \). The function can be written as: \[ D(t) = 40 + 10 \cos\left(\frac{2\pi}{12.5}t\right) \] Where: - \( D(t) \) represents the depth of the water \( t \) hours after high tide. - \( 40 \) is the midline, representing the average depth. - \( 10 \) is the amplitude. - \( \cos\left(\frac{2\pi}{12.5}t\right) \) represents the cosine wave over the period of 12.5 hours. This function provides a mathematical model for predicting the harbor's water depth at any given time after high tide.
Expert Solution
Step 1

Given,

High tide=50 feet

Low tide=30 feet

t=0 is high tide occurs at 12.5 hours

Period=24 (one complete day)

 

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