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Thread: 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; Jan 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 $\displaystyle \pi\pm 2n\pi$

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

    The $\displaystyle \pm 2n\pi$ 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 $\displaystyle \sin bx$ and $\displaystyle \cos bx$ is $\displaystyle \frac{2\pi}{b} $

    The solution for $\displaystyle \sin x = 1 \implies x = \frac{\pi}{2}$ 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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