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Math Help - vector calculus

  1. #1
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    vector calculus

    for each expression, determine whether or not it makes sense..explain

    a*(b*c) ..the back of the book says this doesn't make sense but i don't know why..
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  2. #2
    MHF Contributor Calculus26's Avatar
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    you can aonly take the dot product of a vector with a vector

    a*(b*c)

    b*c is a scalar (number)

    so you can't take the dot product of the vector a with a nunber
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  3. #3
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    thanks so its the same thing with
    (a*b)/c then? because a*b is a number
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  4. #4
    MHF Contributor Calculus26's Avatar
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    no --- iit makes no sense because you can't divide by a vector-- there is no such operation.

    if c were a constant(a*b)/c is just a number over a number which would makes sense
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  5. #5
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    ohh okay..so my last one is
    (the magnitude of a)^2 * b - (a*b)^2 *a
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  6. #6
    MHF Contributor Calculus26's Avatar
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    Same reason as the first

    (the magnitude of a)^2 * b - (a*b)^2 *a


    (the magnitude of a)^2 is a scalar

    (a*b)^2 is a scalar

    again you can't take the dot product of a scalar and a vector
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  7. #7
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    the back of the book says its right though..hmm. oh well. thank you for all of your help with everything!! youre the best
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  8. #8
    MHF Contributor Calculus26's Avatar
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    you can take a scalar times a vector but not the dot product of a scalar

    with a vector

    so if the question was (|a|^2)b without the dot it makes sense


    Similarly[(a*b)^2]a would make sense if you are not talking about the dot product
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  9. #9
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    thank you!
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