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Homework Help: Help on expanding this equation

  1. Dec 5, 2005 #1
    hello.. i've been having some trouble with expanding this:

    (B^2+C^2)^(1/2) X sin (omega*t +(taninverse B/C)

    (read as: square root of (b squared plus c squared) times sin times the quantity omega times t plus taninverse of B divided by C)

    apparently, the answer is supposed to be B cos omega*t + C sin omega*t .. but i've gotten like B arctan omega^2(t) + C cos omega*t... i just wanted to know like the way to get the answer.. i think i'm using trig identities incorrectly..
  2. jcsd
  3. Dec 5, 2005 #2


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    What you need is [itex]\sin (x + y) = \sin x \cos y + \cos x \sin y[/itex] and use the fact that [itex]\sin \tan^{-1} x = x/ \sqrt {1 + x^2}[/itex] and similarly for the cosine.
  4. Dec 5, 2005 #3
    thanks! that helped a lot! thank you!
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