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Math Help - Please check my answer (Newton's Method)

  1. #1
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    Please check my answer (Newton's Method)

    Find the smallest positive value which satisfies x = 2.600cos(2.400x)

    I used the formula

    xn+1 = xn + [2.600cos(2.400xn)-xn]/[6.240sin(2.400xn)-1]

    I ended up with x = 0.4900 after a few runs through but my online homework tells me this is incorrect. My calculator seems to get close to this when I use the zoom function to check though.
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  2. #2
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    Your equation just one simple error. I see you have made it plus [xn + f(x)/-f'(x)], in substitution for the denominator having reversed signs. But you also need to reverse the sign for the '1' at the end as well.

    x_{n+1} = x_n + \dfrac{2.6 \cos(2.4x_n)-x_n}{6.24 \sin(2.4x_n)+1}
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  3. #3
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    Ah, thanks! That solves numerous problems throughout my homework, lol.
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