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Homework Help: Cross product

  1. Dec 9, 2011 #1
    Prove A x (B + C) = A x C + A x B

    Related equations:
    Cross product

    Not even remotely sure where to start with this, other than I need to use the cross product rule.
  2. jcsd
  3. Dec 9, 2011 #2
    Try defining each vector [tex] (a_1, a_2, a_3), (b_1, b_2, b_3), (c_1, c_2, c_3) [/tex] and then using the defintion of the cross product in each case.
  4. Dec 13, 2011 #3
    i have to ask that using Sinθ=u x v/|u||v|, these both vectors are 2-Dimensional u=-3i-5j,
    v=4i+7j, u x v=-21i+20j ,|u|=√34,|v|=√65, Sinθ=-21i+20j/(√65√34)
    question is check are they parallel?plz can anyone help me for the last step
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