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Math Help - Check my work regarding vector projection?

  1. #1
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    Check my work regarding vector projection?

    Sorry if this is the wrong section, but it came from my Calc book.

    Given: a = 3i - 4j - k and b = 2i + 5k

    Are these answers correct?

    a) a dot b = 1
    b) component of a in the direction of b = 1/\sqrt{29}
    c) projection of a in the direction of b = < 2/29, 0, 5/29 >
    d) component of b in the direction of a = 1/\sqrt{26}
    e) projection of b in the direction of a = < 3/26, -2/13, -17/26 >
    Last edited by Mattpd; June 30th 2010 at 04:16 PM.
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  2. #2
    Junior Member
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    Oct 2009
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    a) Yes, you are correct.

    b) Correct.

    c) Correct.

    d) Again, correct

    e) I'm not entirely sure how you obtained those numerators. I found the vector projection to be  b_{a}=\frac{3}{26}\vec{i} -\frac{4}{26}\vec{j}-\frac{1}{26}\vec{k}, using the formula b_{a}=\frac{a \bullet b}{|b|^2}a. Using the same formula, you're answer to c is right. So, I'm not sure what you did. Feel free to point out something I did wrong.
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