Area of a triangle using vectors

  • Thread starter Calpalned
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  • #1
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## 1. Homework Statement
Let P = (1,1,1), Q = (0, 3, 1) and R = (0, 1, 4). Find the area of triangle PQR

Homework Equations


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

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. ##
 

Answers and Replies

  • #2
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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?
 
  • #3
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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?
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.
 
  • #4
SammyS
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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.
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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