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Homework Help: Writing a trig product

  1. Oct 5, 2005 #1
    I have to write [tex] {\it sina}+{\it sinb}+\sin \left( a+b \right) [/tex] as a product.
    Here is what I began with, then I got stuck...
    [tex] 2\,\sin \left( (a+b)/2 \right) \cos \left( (a-b)/2 \right) +{\it sina}\,{\it cosb}+{\it cosa}\,{\it sinb} [/tex]

    Anyone please can help me out, that would be great, thank you! :smile:
  2. jcsd
  3. Oct 6, 2005 #2


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    tatoo5ma, Instead of expanding sin(a+b), what else can you do? If you write it as a trignometric function of (a+b)/2 can you see what happens?
    Last edited: Oct 6, 2005
  4. Oct 6, 2005 #3


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    Sin (a+b) = Sin (2(a+b)/2) = 2 cos((a+b)/2)Sin((a+b)/2)
  5. Oct 6, 2005 #4
    yeah, then u can factor with Sin((a+b)/2) and then make cos((a-b)/2)+cos((a+b)/2) equal to 2cos(a/2)cos(b/2) and u have everythin factorized :smile:
    Last edited: Oct 6, 2005
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