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Homework Help: Makes no sense as theta is obviously obtuse

  1. Jul 8, 2012 #1
    348q88w.png

    Working for a)

    Resolving upwards:

    12cos(θ -90) - 8 = 0
    cos(θ-90) = sinθ
    12sinθ = 8
    sinθ = 2/3
    θ = 41.8 (3.sf)

    This makes no sense as theta is obviously obtuse, if I don't simplify to sinθ I get:

    cos(θ-90) = 2/3
    θ = 48.2... + 90
    = 138.2 (1.dp)

    Why does it not work if I simplify to sinθ?
     
  2. jcsd
  3. Jul 8, 2012 #2
    Re: Statics

    sinθ = 2/3 has an infinite number of solutions, what are some others?
     
  4. Jul 8, 2012 #3
    Re: Statics

    180 - θ

    silly me, thanks.
     
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