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Math Help - Solving trig Equations

  1. #1
    Member >_<SHY_GUY>_<'s Avatar
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    Unhappy Solving trig Equations

    I need help on these questions...i really dont get them:

    solve:
    cosx (cosx-1)=0

    and these next two are on the inerval of [0, 2pi)

    2sin^2x = 2+cosx

    secx + tanx=1

    and theres one on harmonic motion i dont get:

    the position of the weight relative to the point of equilibrium is given by:
    y= 1/12 (cos8t-3sin8t)
    find the times when the weight is at the point of equilibrium (y=0) for 0 is less than/ equal to t that is less than/equal to 1.

    Thanks!
    Last edited by >_<SHY_GUY>_<; May 5th 2008 at 05:24 PM. Reason: forgot additional info
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  2. #2
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    Quote Originally Posted by >_<SHY_GUY>_< View Post
    I need help on these questions...i really dont get them:

    solve:
    cosx (cosx-1)=0


    \cos{x}(\cos{x-1})=0

    Set each of the factors equal to zero because anything times zero, equals zero..right?


    \cos{x}=0

    We know that cosx=0 for \frac{\pi}{2} and \frac{3\pi}{2}. Generalizing that to include their multiples we have:

    x=\frac{\pi}{2}\pm\pi k

    Now try it with the other factor:

    \cos{x}-1=0

    Add one to each side, then think about the unit circle to determine for what values cosx=1. Remember, on this one you want to solve for all values, not just from 0 to 2\pi.
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