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Homework Help: Trig function question

  1. Dec 1, 2008 #1
    1. The problem statement, all variables and given/known data
    The depth, d, of the tide in a bay is modelled by the formula
    d=A+Bcos(Ct+D) where A,B,C and D are constants, d is measured in metres and t in hours.

    The time between successive high tides is 14 hours. The maximum depth of the tide in the bay is 5 m and the minimum depth is 1m. Initially the depth is 4m and the tide is coming in

    Find A,B,C and D

    How do I do this?
  2. jcsd
  3. Dec 1, 2008 #2


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    Homework Helper

    For the function d=A+Bcos(Ct+D), when d=5, the function is maximum, are you able to find an equation in A and B only from this?

    (Hint: cos(t) has a maximum of 1 regardless of t, thus for cos(Ct+d), will have a maximum of ?)

    Similarly for d=1, it has a minimum value.
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