The water level at a local pier rises and falls with the tide. Yesterday, the maximum depth of the water
at the pier was 8 feet, and the minimum depth was 4 feet. High tide occurred at 12:00 AM and low tide
occurred at 12:20 PM. Which function models the depth, in feet, of the water at the pier yesterday, as a
function of time t in minutes past high tide?

Respuesta :

Answer:

The function  is  [tex]D = 2sin ( \frac{\pi}{2} - \frac{\pi}{12} t) + 6[/tex]

Step-by-step explanation:

From the question we are told that

    The  maximum depth is [tex]d = 8 \ ft[/tex]

      The  minimum depth is  [tex]d_i = 4 \ ft[/tex]

Generally the average depth is mathematically represented as

       [tex]d_a = \frac{8 + 4}{2}[/tex]

=>   [tex]d_a = 6 \ ft[/tex]

Generally  the amplitude is mathematically represented as

      [tex]A = d - d_a[/tex]

=>    [tex]A = 8 - 6[/tex]

=>    [tex]A = 2[/tex]

Generally the period is  24 hours given that the the interval between the maximum depth and the minimum depth is half a day

Generally the period is mathematically represented as

         [tex]T = \frac{2 \pi }{w}[/tex]

here w is the angular  frequency

So

     [tex]w = \frac{2 \pi}{24}[/tex]

      [tex]w = \frac{\pi}{12}[/tex]

Generally the depth can be modeled with a sin function as follows

     [tex]D = Acos (wt) + d_a[/tex]

Now  from co-function identity we have  that [tex]for \ cos (z) = sin (\frac{\pi}{2} - z)[/tex]

So  

     [tex]D = Asin ( \frac{\pi}{2} - wt) + d_a[/tex]

     [tex]D = 2sin ( \frac{\pi}{2} - \frac{\pi}{12} t) + 6[/tex]

   

     

The function that models the depth, in feet, of the water at the pier yesterday, as a function of time t in minutes past high tide is; D = 2 sin((π/2) - (π/12)t) + 6

We are given;

  • Maximum depth; d2 = 8 ft
  • Minimum depth; d1 = 4 ft

Thus;

Average depth; d = (d1 + d2)/2

d = (4 + 8)/2

d = 6 ft

Now, to find the amplitude, we will just subtract the minimum depth from the maximum one to get; A = d2 - d1

A = 8 - 6

A = 2 ft

Now, the period T is a whole day which is 24 hours and so we can find the angular frequency ω from the formula;

ω = 2π/T

Thus;

ω = 2π/24

ω = π/12

  • Now, the general formula for the depth function is given as; D = A sin(π/2 - ωt) + d

Where;

d_i is average depth

Thus;

D = 2 sin((π/2) - (π/12)t) + 6

Read more about sinusoidal functions at; https://brainly.com/question/2410297