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Math Help - Graffing sine and cosine functions?

  1. #1
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    Graffing sine and cosine functions?

    Can anyone explain to me how to do this as I am confused?

    Find the values of angle which each equation is true
    1. cos= -1
    The back of the book says the answer is pi+ 2pi(n)
    Know I know the cos of pi which is 180 degrees is -1
    But I am confused on how to get 2pi(n)
    Last edited by homeylova223; January 8th 2011 at 11:09 AM. Reason: title spelled wrong
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  2. #2
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    Sorry I spelled graphing wrong
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  3. #3
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    180 + 360 degrees is the same thing as 180 degrees (rotate a whole circle once)
    so is 180 + 360n.
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  4. #4
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    The books answer is correct \pi\pm 2n\pi

    \cos x =-1 has repeated solutions given the nature of the function.

    The \pm 2n\pi part comes from the period of the function and where the solution repeats, do you know how to find the period?
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  5. #5
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    No I am not sure how to find the period. Can you also show me how you would do sin angle=1?
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  6. #6
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    Quote Originally Posted by homeylova223 View Post
    No I am not sure how to find the period. Can you also show me how you would do sin angle=1?
    The period of \sin bx and \cos bx is \frac{2\pi}{b}

    The solution for \sin x = 1 \implies x = \frac{\pi}{2} Now what is the period?
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  7. #7
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    The period is 2pi. I see know because it repeat itself every 2pi I was looking at a chart from my book and your example and I just noticed that. So in order to test my understanding would sin angle=1 be pi/2+pi(n)?
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  8. #8
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    Take a look at the graph of cosx. That should help you.

    y=cosx
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