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Math Help - Find formula from table?

  1. #1
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    Question Find formula from table?



    Alright so I found the mid line to be 15 and amp to be 3.
    The formula I got is f(t) = 3 sin ((pi/10)x) + 15
    However according to the back of the book it got;
    f(t) = 3 sin ((pi/6)(t - 74) + 15

    My question is how did they got that formula from? How did they get a B of pi/6? I am really confused about that part. Everything else on the formula I am ok with. Please help me!
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  2. #2
    Member mathemagister's Avatar
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    Quote Originally Posted by krzyrice View Post


    Alright so I found the mid line to be 15 and amp to be 3.
    The formula I got is f(t) = 3 sin ((pi/10)x) + 15
    However according to the back of the book it got;
    f(t) = 3 sin ((pi/6)(t - 74) + 15

    My question is how did they got that formula from? How did they get a B of pi/6? I am really confused about that part. Everything else on the formula I am ok with. Please help me!
    What you are calling "B" is \frac{2\pi}{\text{period}}

    If you look at the table you will notice that the P-values go above the principal axis for a while, then below, and finally come back to 14 at t=86. That point would be the start of the next period, so you would define the first period from t=73 to t=85.

    So, the period is 85-73 = 12

    \therefore b=\frac{2\pi}{12} = \frac{\pi}{6}

    Hope that helps

    Mathemagister
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