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Math Help - Please help!!! 2 vector problems! (Cross product)

  1. #1
    cyy
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    Please help!!! 2 vector problems! (Cross product)

    Let a = [ 1, 1, 0 ], b = [-1, 2, 0 ], c = [ 2, 3, 1 ], d = [ 5, -7, 2 ]


    Q1. b x ( b x c )
    Q2. ( a - b ) x ( a - c ) + d

    May I know how should I solved above?


    Best regards
    cyy
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  2. #2
    Flow Master
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    Quote Originally Posted by cyy View Post
    Let a = [ 1, 1, 0 ], b = [-1, 2, 0 ], c = [ 2, 3, 1 ], d = [ 5, -7, 2 ]


    Q1. b x ( b x c )
    Q2. ( a - b ) x ( a - c ) + d

    May I know how should I solved above?


    Best regards
    cyy
    Q1 Many approaches. You can calculate a = b x c and then calculate b x a. Or you can use the formula for the vector triple product: Vector Triple Product -- from Wolfram MathWorld (then you only have to calculate scalar products).

    Q2 Get e = a - b and f = a - c. Now calculate e x f. Add d to the result.

    You should know how to calculate a cross/vector product ....


    Slightly off-topic but this thread is too good an opportunity to pass up:

    Question: What do you get when you cross a mountain-climber with a mosquito?
    Answer: Nothing - You can't cross a scaler with a vector.
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  3. #3
    cyy
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    Thx for your help!!! very appreciate for ur effort!
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