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Bisection (trigonometry)

  1. Jul 3, 2007 #1
    [tex]cos(2x)=2cos^2(x)-1[/tex]
    what algebrical rule guarantees me thet is right to divide both angles for 2:
    [tex]cos(x)=2cos^2(x/2)-1[/tex]
     
  2. jcsd
  3. Jul 3, 2007 #2

    uart

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    Science Advisor

    Substitution, nothing more.

    [tex]cos(2x)=2cos^2(x)-1[/tex]

    Let u=2x, then

    [tex]cos(u)=2cos^2(u/2)-1[/tex]

    Now you can replace u with whatever pronumeral you desire.
     
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