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Homework Help: Cosine functions and tides

  1. Dec 28, 2011 #1
    1. The problem statement, all variables and given/known data

    High tide at 4am with a depth of 6 meters. Low tide at 10 am with a depth of 2 meters. Model the problem using the equation to show the depth of the water t hours after midnight.

    2. Relevant equations

    y= A cos(Bx+C) +D

    3. The attempt at a solution: I am not getting the values that I should I think.

    I have A=2, D=4, B=pi/6, C=pi/6. They don't seem right though.
  2. jcsd
  3. Dec 28, 2011 #2


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    No, it's not right. Your C value is wrong. You need to have Bx+C equal to 0 when x=4 and equal to pi when x=10.
    Last edited: Dec 28, 2011
  4. Dec 28, 2011 #3
    Ok. thanks Dick. I got -2pi/3 for a better answer for C.
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