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Math Help - find sine and cosine

  1. #1
    Member smmmc's Avatar
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    find sine and cosine

    Hi,

    1)27pi/2

    : sin (13pi + pi/2)
    =1
    so cos=0

    2)11pi/2

    :sin(5pi + pi/2)
    =1
    so cos=0

    i used the unit circle to figure this out

    Thanks
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  2. #2
    MHF Contributor
    Prove It's Avatar
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    Quote Originally Posted by smmmc View Post
    Hi,

    1)27pi/2

    : sin (13pi + pi/2)
    =1
    so cos=0

    2)11pi/2

    :sin(5pi + pi/2)
    =1
    so cos=0

    i used the unit circle to figure this out

    Thanks
    What you've posted is a lot of nonsense.

    \sin is meaningless unless it is written as the sine of an angle.

    So is \cos.
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  3. #3
    MHF Contributor red_dog's Avatar
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    \sin\left(13\pi+\frac{\pi}{2}\right)=\sin\left(12\  pi+\pi+\frac{\pi}{2}\right)=

    =\sin\left(\pi+\frac{\pi}{2}\right)=-\sin\frac{\pi}{2}=-1

    Similarly, \sin\left(5\pi+\frac{\pi}{2}\right)=-1
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  4. #4
    Member smmmc's Avatar
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    Thank You Red Dog.
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  5. #5
    MHF Contributor

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    Quote Originally Posted by Prove It View Post
    What you've posted is a lot of nonsense.

    \sin is meaningless unless it is written as the sine of an angle.

    So is \cos.
    What you've written is non-sense. Sine and cosine are often used in mathematics in ways that have nothing to do with angles.

    Sine and cosine are commonly introduced in basic trigonometry courses but you should have learned other definitions, that, again, have nothing to do with angles, in, say, secondary school.
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  6. #6
    Senior Member
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    Can you explain it more halls?

    thx
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