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Homework Help: Trig Equations

  1. Jul 21, 2008 #1
    I'm having trouble starting off with these equations:

    sinx(sin x + 1) = 0

    I can solve sin x + 1 =
    Sin x = -1
    x = -90

    but then I don't know how to find all the solutions. Can someone please explain it to me. Thanks.
     
  2. jcsd
  3. Jul 21, 2008 #2

    Astronuc

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    Staff Emeritus
    Science Advisor

    if h(x) = f(x)g(x), then h(x) = 0 if either f(x) = 0 or g(x) = 0, or f(x) = g(x) = 0, i.e. they have a common root.

    Based on sinx (sin x + 1) = 0

    one can have two possibilities: sin x = 0 and sin x = -1.

    Consider if sin x = a, then x = sin-1 (a), and remember that sin is a periodic function, i.e. sin x = sin (pi - x) and sin x = sin (x + 2pi).
     
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