A volume of a tetrahedron

In summary, The conversation discusses finding the minimal volume of a tetrahedron constructed by a plane that crosses over a given point and the axis planes. The formula for the side of the tetrahedron is given, but there is uncertainty about its correctness as it results in a volume of 0. The conversation then introduces an equation for a plane that crosses the axes at (a, 0, 0), (0, b, 0), and (0, 0, c) and asks for the volume of the tetrahedron formed by this plane. To satisfy the constraint of passing through the given point, the formula for the volume of the tetrahedron is minimized in terms of a, b,
  • #1
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i have the point P(x0,y0,z0) i need to find the minimal volume of a tetrahedron which is constructed by a plane which crosses over point P, and by the axis planes.

i got that the side of the tetrahedron is sqrt[(x-x0)^2+(y-y0)^2+(z-z0)^2], but I am not sure it's correct because then the answer is that the volume of the tetrahedron is 0.

your help is appreciated.
 
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  • #2
The plane that crosses the axes at (a, 0, 0), (0, b, 0), and (0, 0, c) has equation x/a+ y/b+ z/c= 1 (do you see why that's obvious?). What is the volume of that tetrahedron? Of course, to pass through the point (x0,y0,z0), it must also satisfy
x0/a+ y0/b+ z0/c= 1.

So, minimize that formula for volume of a tetrahedron (in terms of a, b, c) subject to that constraint.
 
  • #3
HallsofIvy said:
The plane that crosses the axes at (a, 0, 0), (0, b, 0), and (0, 0, c) has equation x/a+ y/b+ z/c= 1 (do you see why that's obvious?). What is the volume of that tetrahedron? Of course, to pass through the point (x0,y0,z0), it must also satisfy
x0/a+ y0/b+ z0/c= 1.

So, minimize that formula for volume of a tetrahedron (in terms of a, b, c) subject to that constraint.
can you tell me how did you arrive at the equation?
cause from what i can remember, you start by constructing vectors from the three points:
(a,0,-c),(a,-b,0),(0,-b,c) and then you substract them and you get the next parameter equation:
(0,-b,c)+s(-a,0,c)+t(-a,-b,2c)
and then multiply by coeffiecient vector (A,B,C), and then plug in (0,-b,c)
which i get the next equation:
x/a+y/b+z/c=0 without the 1, where did i get it wrong?
 

1. What is a tetrahedron?

A tetrahedron is a three-dimensional geometric shape with four triangular faces, six edges, and four vertices.

2. How is the volume of a tetrahedron calculated?

The formula for calculating the volume of a tetrahedron is V = (a^3 * √2) / 12, where a is the length of one of the edges.

3. Can the volume of a tetrahedron be negative?

No, the volume of a tetrahedron cannot be negative. It is a measure of the amount of space enclosed by the shape, and space cannot have a negative value.

4. What is the unit of measurement for the volume of a tetrahedron?

The unit of measurement for the volume of a tetrahedron can vary depending on the unit of measurement used for the length of the edges. It could be cubic centimeters, cubic inches, or any other unit of volume.

5. What is the practical application of calculating the volume of a tetrahedron?

Calculating the volume of a tetrahedron can be useful in various fields such as architecture, engineering, and geometry. It can help in determining the amount of material needed for a project or the capacity of a container with a tetrahedral shape.

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