Area of a triangle in 3 space using cross product

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SUMMARY

The area of a triangle in 3D space can be calculated using the formula 1/2||axb||, where a and b are vectors representing two sides of the triangle. It is established that the order of the vectors does not affect the result; thus, any combination of the vectors formed by the triangle's vertices (ab, bc, ac) will yield the same area. Specifically, if vectors a, b, and c are defined such that c = a + b, the area remains consistent across different vector pairings due to the properties of the cross product.

PREREQUISITES
  • Understanding of vector mathematics
  • Familiarity with the cross product operation
  • Knowledge of vector norms
  • Basic principles of geometry in three-dimensional space
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  • Study the properties of the cross product in vector algebra
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jlemus85
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Hi all, I have a general question.

When calculating the area of a triangle in 3 space, one applies the formula

1/2||axb||. Given three vertices, a,b,c...does it matter which vectors we choose to use (ab, bc, ac) as our a b vectors?

Thanks!
 
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First, because of the norm, it does not matter which is a and which is b: that is (1/2)||axb||= (1/2)||bxa||. That is, order doesn't matter. Now if a, b, and c are vectors forming a triangle, then c= a+ b so (1/2)||axc||= (1/2)||ax(a+b||= (1/2)||axa+ ab|= (1/2)||axb|| because axa= 0. In other words, all combinations give the same result.
 

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