Math Problem Statement

The location of an object moving along the number line at time t seconds is given by

d(t) =

100

5 + 4 sin(t)

where t is assumed to be non-negative. (h) On the time interval [4,15], what is maximum distance from the origin to the object?

Solution

To find the maximum distance from the origin to the object on the time interval [4,15][4, 15], we need to maximize the function:

d(t)=1005+4sin(t)d(t) = \frac{100}{5 + 4 \sin(t)}

Steps:

  1. Find the derivative d(t)d'(t): We'll use the quotient rule to differentiate d(t)d(t). The quotient rule is:

    ddt(f(t)g(t))=f(t)g(t)f(t)g(t)g(t)2\frac{d}{dt} \left( \frac{f(t)}{g(t)} \right) = \frac{f'(t)g(t) - f(t)g'(t)}{g(t)^2}

    Here, f(t)=100f(t) = 100 (a constant) and g(t)=5+4sin(t)g(t) = 5 + 4 \sin(t). So:

    • f(t)=0f'(t) = 0
    • g(t)=4cos(t)g'(t) = 4 \cos(t)

    Applying the quotient rule:

    d(t)=0(5+4sin(t))1004cos(t)(5+4sin(t))2d'(t) = \frac{0 \cdot (5 + 4 \sin(t)) - 100 \cdot 4 \cos(t)}{(5 + 4 \sin(t))^2}

    Simplifying:

    d(t)=400cos(t)(5+4sin(t))2d'(t) = \frac{-400 \cos(t)}{(5 + 4 \sin(t))^2}

  2. Set d(t)=0d'(t) = 0 to find critical points:

    The derivative is zero when the numerator is zero:

    400cos(t)=0-400 \cos(t) = 0

    This simplifies to:

    cos(t)=0\cos(t) = 0

    The values of tt where cos(t)=0\cos(t) = 0 are:

    t=π2,3π2,5π2,t = \frac{\pi}{2}, \frac{3\pi}{2}, \frac{5\pi}{2}, \dots

    In the interval [4,15][4, 15], the relevant values of tt are approximately:

    t=3π24.71andt=7π210.99t = \frac{3\pi}{2} \approx 4.71 \quad \text{and} \quad t = \frac{7\pi}{2} \approx 10.99

  3. Check the endpoints and critical points:

    We now evaluate d(t)d(t) at the critical points and the endpoints t=4t = 4 and t=15t = 15:

    • At t=4t = 4:

      d(4)=1005+4sin(4)1005+4(0.7568)=10053.0272=1001.972850.68d(4) = \frac{100}{5 + 4 \sin(4)} \approx \frac{100}{5 + 4( -0.7568)} = \frac{100}{5 - 3.0272} = \frac{100}{1.9728} \approx 50.68

    • At t=15t = 15:

      d(15)=1005+4sin(15)1005+4(0.6503)=1005+2.6012=1007.601213.16d(15) = \frac{100}{5 + 4 \sin(15)} \approx \frac{100}{5 + 4(0.6503)} = \frac{100}{5 + 2.6012} = \frac{100}{7.6012} \approx 13.16

    • At t=3π24.71t = \frac{3\pi}{2} \approx 4.71:

      d(3π2)=1005+4sin(3π2)=1005+4(1)=1001=100d\left(\frac{3\pi}{2}\right) = \frac{100}{5 + 4 \sin\left(\frac{3\pi}{2}\right)} = \frac{100}{5 + 4(-1)} = \frac{100}{1} = 100

    • At t=7π210.99t = \frac{7\pi}{2} \approx 10.99:

      d(7π2)=1005+4sin(7π2)=1005+4(1)=100911.11d\left(\frac{7\pi}{2}\right) = \frac{100}{5 + 4 \sin\left(\frac{7\pi}{2}\right)} = \frac{100}{5 + 4(1)} = \frac{100}{9} \approx 11.11

  4. Conclusion:

    The maximum value of d(t)d(t) in the interval [4,15][4, 15] is at t=3π24.71t = \frac{3\pi}{2} \approx 4.71, where the distance is:

    d(3π2)=100d\left(\frac{3\pi}{2}\right) = 100

Thus, the maximum distance from the origin to the object is 100 units.

Would you like further details on any step? Here are 5 related questions to explore:

  1. How would the result change if the interval were extended beyond [4, 15]?
  2. Can you explain why cos(t)=0\cos(t) = 0 gives critical points?
  3. What is the significance of the derivative in finding maximum values?
  4. How does the function sin(t)\sin(t) influence the behavior of d(t)d(t)?
  5. What role do endpoints play in optimization problems?

Tip: Always check both the critical points and the endpoints when looking for absolute maximum or minimum values on a closed interval.

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Math Problem Analysis

Mathematical Concepts

Calculus
Optimization
Trigonometric Functions

Formulas

d(t) = 100 / (5 + 4 sin(t))
Derivative using quotient rule: f'(t) = [f'(t)g(t) - f(t)g'(t)] / g(t)^2

Theorems

Quotient Rule for Derivatives
Critical Points: f'(t) = 0

Suitable Grade Level

College Calculus