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Math Help - Finding a Trig Equation

  1. #1
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    Finding a Trig Equation

    Here is a picture of my question, just click on it to enlarge it. I need the equation to be sin. Here is an example from another question of the format of the formula.

    5sin30(x-1)+7

    And here is the question



    This is extremely urgent, please help out.

    Thanks alot.
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  2. #2
    Eater of Worlds
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    You can run it through Excel or a lot of calculators and they'll do sine regressions. I used my ol' TI-92 and got:

    y=1.085605sin(.907418x+.209669)-0.229008

    For the second part of the problem, set the equation equal to 0.5 and solve for x.
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  3. #3
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    K, i tried it and it didnt give the proper output numbers. I need the formula to include the axis, amplitude etc, if that helps.
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  4. #4
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    That's all in your equation.The amplitude is obviously 1.085605.

    The equation I gave gives the proper output. Not right on the money, but very close. That is as close as you can get.

    For instance, if x=1.25, we get .829

    Compare to .83 That's good.
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  5. #5
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    It dosent work... For .5 i get a -21. The amplitude should equal .425... and there is no phase shift so i dont know what youre doing.
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  6. #6
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    Not begging for an answer but this needs to be answered within about 6 hours.
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  7. #7
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    Are you sure you're not in degrees. When I use .5, I get .439

    .45 is what is in the chart. That is very close. Looking again, I do not see anything wrong. The data matches very close.

    Using my equation we get

    0 is -.003

    .5 is .44

    .75 is .61

    1.25 is .83

    2.25 is .61

    3 is -.003

    I do not know how you got -21 for x=.5

    Those look close to me.

    I suppose I am misunderstanding.

    If you have something like y=a\cdot{sin(bx+c)}, then the period is \frac{2\pi}{|b|} and the phase shift is \frac{-c}{b}. The amplitude is |a|
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