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Math Help - area of parallelogram

  1. #1
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    area of parallelogram

    Find the area of the parallelogram with vertices (5,1), (8, 6), (12, 9), and (15, 14)
    How would I start this problem?
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  2. #2
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    have a look how it's done ...

    Area of Parallelogram from Vector Cross Product
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  3. #3
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    thank you that is very useful but i must be doing something wrong in my calculations the vector i get from those points are 3i+5j+0k for both, when i take the cross product the answer is 0. I know that is not correct. What's wrong with my calculations
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  4. #4
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    Allie, a sketch always helps. What you're doing is... You're finding the vector of a diagonal of the parallelogram BC instead of the adjacent side, AC. Calculate the vector product \vec{AB}\times\vec{AC}.

    I hope that helps.

    ILoveMaths07.
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  5. #5
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    haha the sketch does not help i don't even see parallelogram in the sketch, it looks like a straight line
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  6. #6
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    not a line, but a very "skinny" parallelogram

    two adjacent sides ...

    (5,1) to (8,6) and (5,1) to (12,9)

    first side vector ... u = 3i + 5j

    adjacent side vector ... v = 7i + 8j

    now find the cross product.
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  7. #7
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    ok i got it now thank you

    Now would i do the same for this problem?
    Find the volume of the parallelepiped defined by the vectors

    (5,2,1) (-3,-2,5) (2,5,-2)
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  8. #8
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  9. #9
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    thank you that website is very helpful
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