Sloving triangles in 3d

  • Thread starter uf2010
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  • #1
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How do i find the angles in the triangle with the vertices at [2,-1,0], [5,-4,3], and [1,-3,2]. This problem has been bothering me because when i find the angle between the vectors it only adds to roughly 110 degrees, and that cannot be right.
 

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  • #2
nicksauce
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To find the angle between two vectors you can use

[tex]u\cdot v=|u||v|\cos{\theta}[/tex]
 
  • #3
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I have tried this, but the sum of the three angles only equals 110 not 180.
 
  • #4
Defennder
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nicksauce's approach should work here. You should be careful of the directions the vectors point and the angle between them. The angle between the tail of a vector and and the head of another vector is not the same as the one given by the dot product.
 
  • #5
Defennder
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Another way which doesn't involve vectors would be to find the lengths of the triangle by calculating distance between points, then apply cosine rule. A purely geometrical approach.
 

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