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Calculating complex cos curves from data

  1. Mar 9, 2009 #1
    1. The problem statement, all variables and given/known data

    i have to create a mathematical forumal from data of high and low tide depths and times. from that predict the next weeks outcome.
    it has to have sin or cos in the equation. a*COS (bx+c)+d or sin.

    this is the data given
    Mon 09/03/2009 Tue 10/03/2009 Wed 11/03/2009 Thu 12/03/2009 Fri 13/03/2009
    Low 12:22am 0.22m Low 1:09am 0.16m Low 1:54am 0.15m Low 2:36am 0.2m Low 3:18am 0.3m
    High 6:50am 1.98m High 7:32am 1.99m High 8:11am 1.95m High 8:47am 1.85m High 9:22am 1.72m
    Low 1:17pm 0.29m Low 1:54pm 0.22m Low 2:29pm 0.19m Low 3:01pm 0.2m Low 3:32pm 0.23m
    High 7:10pm 1.56m High 7:53pm 1.66m High 8:34pm 1.74m High 9:14pm 1.77m High 9:53pm 1.76m

    i was thinking of adding 2 different a*COS (bx+c)+d together as it seems to have two main curves going with it. therers the more obvious one and then a subtle one which makes the amplitudes of waves bigger. so i thought i could find information on full moons, new moons, solar eclipses, etc and use that to caluclate a formula.

    but i have no idea

    i think other people are using a function on their calculator to create it
    but i have no idea what.


    im not asking for you to work it out, the data is pretty hard to read in this format. Im just asking for a method!!! or a websites or program that can calculate it.
    anything. im so desperate.
    Last edited: Mar 9, 2009
  2. jcsd
  3. Mar 9, 2009 #2


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    Homework Helper

    Intuitively you know that the fullness of the moon will correlate in some way with the maximum of the tides. Where you are in the cycle and the number of degrees of off set, you will need to fiddle with to determine.

    As to heights I suspect that a coefficient off of that with the same period will be able to say something about the heights of your tides as well as the timing.
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