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Solve give me some help

  1. Feb 27, 2005 #1
    Solve plz give me some help

    how would you solve this question cos2x+cosx+1=0? The cos2x is throwing me off is that the same as cos^2x? Its multiple choice and all the answers are in radian how come?
     
    Last edited: Feb 27, 2005
  2. jcsd
  3. Feb 27, 2005 #2

    AKG

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    1. cos(a + b) = cos(a)cos(b) - sin(a)sin(b).
    2. Do you know how to write 1 in terms of sin and cos?
     
  4. Feb 27, 2005 #3
    no i dont plz help me
     
  5. Feb 27, 2005 #4
    [tex]\sin^{2}x + \cos^{2}x = 1[/tex]
     
  6. Feb 27, 2005 #5
    cos2x is not the same as cos^2x. Use a double angle identity for that one.
     
  7. Feb 28, 2005 #6

    dextercioby

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    On normal basis,u should end up with a simple quadratic equation is "\cos x"...That won't be 2 hard to solve...

    Daniel.
     
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