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Area of a triangle using vectors

  1. Feb 18, 2015 #1
    ## 1. The problem statement, all variables and given/known data
    Let P = (1,1,1), Q = (0, 3, 1) and R = (0, 1, 4). Find the area of triangle PQR

    2. Relevant equations
    ## \frac {|PQ × PR|}{2} ## = area (The crossproduct divided by two)

    3. The attempt at a solution
    I lost my answer key, so I want to check if my final answer of ## \frac {\sqrt {13}}{2} ## is right. Thanks everyone. If it isn't, I'll put up my work. ##
     
  2. jcsd
  3. Feb 18, 2015 #2
    Hey there Calpalned. I have worked the problem through, and I am not sure that your answer is correct. Are you sure you have evaluated the cross product correctly?
     
  4. Feb 18, 2015 #3
    I took the cross product of ## <-1, 2, 0> ## and ## <-1, 0,3> ## and I got ## (0-0)-(-3-0)+(0--2) ## = ## <0, 3, 2> ## Taking the magnitude, I get the answer in my first post.
     
  5. Feb 18, 2015 #4

    SammyS

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    Not correct.

    This should have vector components: ## (0-0)-(-3-0)+(0--2) ## . What you have is a scalar.

    The x-component of the result, ##\ <0,\, 3,\, 2>\ ## is incorrect.
     
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