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Homework Help: Trig. Identity

  1. Oct 29, 2009 #1
    1. Verify this identity: a*sin Bx + b*cos Bx = sqrt(a^2 + b^2)sin(Bx + C)
    where C= arctan b/a

    2. a/sqrt(a^2+b^2)sin Bx + b/sqrt(a^2+b^2)cos Bx=cos C sin Bx + sin C cos Bx=

    3.a*sin Bx + b cos Bx = sqrt(a^2 + b^2) sin(Bx + C)

    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    Last edited: Oct 30, 2009
  2. jcsd
  3. Oct 30, 2009 #2


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    Gold Member

    First thing that jumps to my mind is to make use of the trig expansion:

    [tex]R sin(Bx+C)=R(sin(Bx) cos(C)+cos (Bx)sin(C))[/tex]
  4. Oct 30, 2009 #3
    danago thanks for the hint.
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