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Trig sum formulas

  1. Apr 28, 2009 #1
    sin(a + b) = sin(a)cos(b) + cos(a)sin(b)
    sin(a - b) = sin(a)cos(b) - cos(a)sin(b)

    cos(a + b) = cos(a)cos(b) - sin(a)sin(b)
    cos(a - b) = cos(a)cos(b) + sin(a)sin(b)

    Who first derived them? When, and how?

    Thanks
     
  2. jcsd
  3. Apr 28, 2009 #2

    tiny-tim

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    Not how, but Howe … Julia Ward Howe, in 1861, derived them, and they became a Civil War marching song, to the tune now known as the Battle Hymn of the Republic. :wink:
     
  4. Apr 28, 2009 #3
    If it's a joke... sorry but I don't get it.
     
  5. Apr 28, 2009 #4

    tiny-tim

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    :rolleyes:

    try singing it! :smile:
     
  6. Apr 29, 2009 #5
    Struggling to get a nice melody... :P

    Any serious comments?
     
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