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Can addition formula be applied to more than 2 sums?

  1. Oct 17, 2009 #1
    1. The problem statement, all variables and given/known data

    Not an actual problem, but to help solve my homework, would cos(A+B+C)=
    CosACosBCosC-SinASinBSinC (Cos(x+y)=cosxcoxy-sinxsiny)

    I was unsure if this can be applied to multiple digits or only 2.

    I know I could plug in numbers to test, but I was wondering about the logic behind this.
  2. jcsd
  3. Oct 17, 2009 #2


    Staff: Mentor

    No, that's not it.

    Expand cos((A+B) + C) first, and then expand the factors with cos(A+B) and sin(A+B).
  4. Oct 17, 2009 #3
    I see.

    So Cos(A+B+C) =


    then use the value from the first portion in another addition formula with C?
  5. Oct 18, 2009 #4


    Staff: Mentor

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