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Trigonometry Question

  1. Dec 2, 2014 #1
    Why

    ##\sin (A+B) = \sin A \cos B + \cos A \sin B##

    and

    ##\cos (A+B) = \cos A \cos B - \sin A \sin B##

    ???????????
     
  2. jcsd
  3. Dec 2, 2014 #2

    Orodruin

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    The proof of this should be available in any basic textbook on trigonometry or by a simple search in a search engine. I suggest starting here: http://en.wikipedia.org/wiki/Proofs_of_trigonometric_identities
    Please note that Physics Forums is not a substitute for a textbook or intended to spoon feed you basic mathematical facts.
     
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