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Math Help - vector multiplication

  1. #1
    Junior Member winterwyrm's Avatar
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    vector multiplication

    Two vectors are given by a = 9.1i + 1.1j and b = 4.9i + 3.8j. Find (a)|a b|, (b)a b, (c)(a + b) b, and (d) the component of a along the direction of b?
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  2. #2
    o_O
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    What exactly are you having trouble with?

    (a) The cross product is only defined for 3-dimensional Euclidean space. So unless you assume the unit vector k to be 0, you can't perform this operation.

    (b) \bold{a} \cdot \bold{b} = a_{1}b_{1} + a_{2}b_{2}. Just plug it in.

    (c) \bold{a} + \bold{b} = (a_{1} + b_{1}) \bold{i} + (a_{2} + b_{2}) \bold{j}

    (d) The orthogonal projection of a along b is given by: \text{proj}_{\bold{b}}\bold{a} = \frac{\bold{a} \cdot \bold{b}}{\mid \bold{b} \mid ^2} \ \bold{b}
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  3. #3
    Junior Member winterwyrm's Avatar
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    k isn't, but I think I figured it out, since there is no z term, a ton of terms in this one equation cancel out, sorry about that. Thanks for your help on the other three parts though =]
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