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Homework Help: Sine of sum and difference with 3 values

  1. Mar 9, 2012 #1
    1. The problem statement, all variables and given/known data

    sin (90 - θ + λ)

    = sin90cos(θ + λ) - cos90sin(θ + λ)

    = cos(θ + λ)

    The book says cos(θ - λ)

    So are we both right and if so how can I manipulate mine to look like the books answer.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 9, 2012 #2


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    Science Advisor
    Homework Helper

    hi afrocod! :smile:
    no, sin (90 - θ + λ) = sin (90 - (θ - λ))

    = sin90cos(θ - λ) - cos90sin(θ - λ) :wink:
  4. Mar 9, 2012 #3
    Ah my old friend Tim.

    I was surprised that 100's of people looked at this and nobody answered. I suspected this was a super easy question, as you just proved.

    Thank you very much.
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