What are a, b, and c in volume calculations for prisms and pyramids?

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Discussion Overview

The discussion revolves around the definitions and roles of the variables a, b, and c in volume calculations for prisms and pyramids, particularly focusing on their representation as vectors and their geometric implications. The scope includes theoretical aspects of geometry and mathematical reasoning related to volume formulas.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant states that the volume of a triangular prism is calculated using the formula v = ½ |a • b x c|, where a is the length of the prism and b and c are sides of the triangular face.
  • Another participant asserts that a, b, and c are vectors that represent the edges of a parallelogram when originating from the same vertex.
  • A different participant raises a question regarding the volume of a parallelepiped and the volume of a tetrahedron, noting the relationship between their volume formulas.
  • One participant inquires about the outcome of combining tetrahedrons of the same shape and size.
  • Another participant comments on the permutations of vectors in the triple product, suggesting that the absolute value is what matters, along with the condition that they meet at a vertex.
  • A later reply confirms that this understanding also defines the parallelepiped.

Areas of Agreement / Disagreement

Participants express varying interpretations of the roles of a, b, and c, with some agreeing on their vector nature while others question the necessity of specific conditions for their lengths. The discussion remains unresolved regarding the implications of these definitions and their applications in volume calculations.

Contextual Notes

There are unresolved assumptions regarding the geometric configurations of the vectors and their relationships in different volume calculations, as well as the implications of using absolute values in vector products.

PFuser1232
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The volume of a triangular prism is given by:

v = ½ |ab x c|

Where b and c are two of the sides of the triangular face of the prism, and a is the length of the prism.

The volume of a rectangular/parallelogram-based pyramid is given by:

V = ⅓ |a • b x c|

My question is, what are a, b, and c?
Is it necessary, in general, that b and c be the lengths of two of the sides of the base?
 
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they are vectors that are the edges of a parallelogram when placed with tails coming from the same vertex.

tripprod0x_thumb.png
 
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Well this topic regenerated the doubt that was in my mind some time ago.
Volume of parallelopiped is
[a b c]
Then how Volume of tetrahedron is
1/6 [a b c]
 
So the permutations of vectors in the triple product doesn't really matter, provided the absolute value is taken.
What matters is that they should be three vectors meeting at any vertex. Correct?
 
Yes and that defines the parallel piped too.
 

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