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Homework Help: Trigonometric problem

  1. May 25, 2004 #1
    How to solve: sin x + sin 3x + sin 2x = 1 + cos 2x + cos x, give general solution in radians for x.
    How to get start?
    Anyone could help me, please?
     
  2. jcsd
  3. May 25, 2004 #2

    arildno

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    You will need the following identities:
    [tex]\cos^{2}x+\sin^{2}x=1,\cos^{2}x-\sin^{2}x=\cos2x[/tex]
    [tex]\sin(a+b)=\sin(a)\cos(b)+\sin(b)\cos(a)[/tex]
     
  4. May 26, 2004 #3
    I have solved the problem. I have used the identities:
    sin x + sin y = 2 sin (x+y)/2 cos(x-y)/2 and cos 2x = 2 cos^2 (x) - 1.
    With these two identities, it's easy to solve the problem.
     
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