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Math Help - Need help with some of the vector question, especially part c, and e-h

  1. #1
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    Need help with some of the vector question, especially part c, and e-h

    Suppose a point A has co-ordinates (−1, 3, 5), a point B has co-ordinates
    (0, −3, 2), and another point C has co-ordinates (−5, −5, −5).
    (a) Find −→BA and −−→CB.
    BA(1, 0, -7)
    CB(5, 8, 3)
    (b) Find −→BA − 3
    −−→CB.
    (16, 24, 16)
    (c) Use the result of part (b) to write −→BA − 3
    −−→CB as a multiple of the vector (8, 0, 9).??? DON'T GET THIS PART

    (d) Express −−→CB in terms of the standard unit vectors i, j and k.
    -5i-8j-3k
    (e) Use the result of part (a) to find −→AC.
    (f) Verify the triangle inequality: ||−→AB +
    −−→BC|| ≤ ||−→AB|| + ||−−→BC||.
    (g) Find a unit vector pointing in the same direction as −→AB.
    (h) How far is the point C from the origin?
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  2. #2
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    Re: Need help with some of the vector question, especially part c, and e-h

    If you could rewrite your questions using LaTeX, that would be great. For example, use
    Code:
    $\overrightarrow{BA}-3\overrightarrow{CB}$
    for
    \[
    \overrightarrow{BA}-3\overrightarrow{CB}.
    \]
    I don't understand what dashes (sometimes one, sometimes two in a row) are supposed to mean. Also, it is recommended to ask at most two questions in a thread.
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  3. #3
    MHF Contributor

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    Re: Need help with some of the vector question, especially part c, and e-h

    Quote Originally Posted by Fearsword View Post
    Suppose a point A has co-ordinates (−1, 3, 5), a point B has co-ordinates
    (0, −3, 2), and another point C has co-ordinates (−5, −5, −5).
    (a) Find −→BA and −−→CB.
    BA(1, 0, -7)
    CB(5, 8, 3)
    To begin with these are wrong. Pleas show each individual calculation.
    Once you have those wrong, you can't hope to get the rest right.

    B](b) Find −→BA − 3[/B]
    −−→CB.
    (16, 24, 16)
    (c) Use the result of part (b) to write −→BA − 3
    −−→CB as a multiple of the vector (8, 0, 9).??? DON'T GET THIS PART

    (d) Express −−→CB in terms of the standard unit vectors i, j and k.
    -5i-8j-3k
    (e) Use the result of part (a) to find −→AC.
    (f) Verify the triangle inequality: ||−→AB +
    −−→BC|| ≤ ||−→AB|| + ||−−→BC||.
    (g) Find a unit vector pointing in the same direction as −→AB.
    (h) How far is the point C from the origin?
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