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Math Help - Angles between vectors (i, j, k)

  1. #1
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    Angles between vectors (i, j, k)

    find the angles of the triangle formed by the points P(2,-2,5), Q(2,1,7) and R(7,6,-10)

    do i use the dot product for this? which pairs would i use? does anyone know how to do this?

    I got the following angles, are these right?

    between P & Q = 28.8 degrees
    " Q & R = 120 degrees
    " P & R = 127.9 degrees
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  2. #2
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    That is not the way to do it.

    m(\angle QPR) = \arccos \left( {\dfrac{{\overrightarrow {PQ}  \cdot \overrightarrow {PR} }}{{\left\| {\overrightarrow {PQ} } \right\|\left\| {\overrightarrow {PR} } \right\|}}} \right)
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  3. #3
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    i did you way and got all my angles adding upto 195 and i think it should be 180. the angles i got where:

    QPR = 95.4
    QRP = 27.3
    RQP = 73.4

    I must be really dumb lol
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  4. #4
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    Your m(\angle QRP) is incorrect.
    Try again. It is about 11.242deg.
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