How do I solve triangles in 3D with specific vertices?

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Discussion Overview

The discussion revolves around solving a triangle in 3D space defined by specific vertices. Participants explore methods to find the angles of the triangle formed by the points [2,-1,0], [5,-4,3], and [1,-3,2], addressing challenges encountered in calculating these angles.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant questions how to find the angles in a triangle defined by three vertices in 3D space, noting that their calculations yield a total of roughly 110 degrees, which seems incorrect.
  • Another participant suggests using the dot product formula to find the angle between two vectors, indicating a potential method for angle calculation.
  • A participant acknowledges the use of the dot product but points out that their results still do not sum to 180 degrees, raising concerns about the calculations.
  • One reply supports the previous approach but emphasizes the importance of considering the directions of the vectors and clarifies that the angle between the tail of one vector and the head of another may differ from the angle calculated using the dot product.
  • Another participant proposes an alternative method that involves calculating the lengths of the triangle using distances between the points and then applying the cosine rule, suggesting a purely geometrical approach.

Areas of Agreement / Disagreement

Participants express differing views on the methods for calculating angles in the triangle, with no consensus on the correct approach or resolution to the initial problem.

Contextual Notes

Participants have not resolved the discrepancies in their angle calculations, and there may be missing assumptions regarding vector directions and the application of the cosine rule.

uf2010
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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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To find the angle between two vectors you can use

[tex]u\cdot v=|u||v|\cos{\theta}[/tex]
 
I have tried this, but the sum of the three angles only equals 110 not 180.
 
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.
 
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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