In geometry, a trirectangular tetrahedron is a tetrahedron where all three face angles at one vertex are right angles. That vertex is called the right angle of the trirectangular tetrahedron and the face opposite it is called the base. The three edges that meet at the right angle are called the legs and the perpendicular from the right angle to the base is called the altitude of the tetrahedron.
Only the bifurcating graph of the
B3
Metric formulas
If the legs have lengths x, y, z then the trirectangular tetrahedron has the volume
V= | xyz |
6 |
The altitude h satisfies[1]
1 | = | |
h2 |
1 | + | |
x2 |
1 | + | |
y2 |
1 | |
z2 |
The area
T0
T | ||||
|
Using the illustration above designate all 3 of the diagonals shown in the green triangle as | a, b, c | & it doesn't matter which of the 3 diagonals is a or b or c. What does matter is that each diagonal be mated with its corresponding rectangular leg. Each of the diagonals connects with only 2 of the rectangular legs but not the 3rd one. The 3rd one IS the mating rectangular leg for the diagonal you chose. Then the equations shown below work properly.
K=l[ | a2+b2+c2 |
2 |
r]=l[x2+y2+z2r]=l[x2+c2r]=l[y2+b2r]=l[z2+a2r]
Givenl[a,b,cr] Givenl[x,y,zr]
K=l[Constantr] K=l[
a2+b2+c2 | |
2 |
r] K=l[x2+y2+z2r]
Use l[x2+c
2r] x=\sqrt{ | |
2 } c=\sqrt{ | |
K-c | |
K-x2 }
Use l[y2+b
2r] y=\sqrt{ | |
2 } b=\sqrt{ | |
K-b | |
K-y2 }
Use l[z2+a
2r] z=\sqrt{ | |
2 } a=\sqrt{ | |
K-a | |
K-z2 }
Volume of a Tri-Rectangular Tetrahedron & the box it'll fit in.
Vtet=
xyz | |
6 |
Vbox=xyz
Internal height of a Tri-Rectangular Tetrahedron from its point of origin | x,y,z | to its base bounded by | a, b, c |
htet =
xyz | |
\sqrt{ x2y2+z2l[x2+y2r] |
}
Area of the to its base bounded by | a, b, c | [2 formulas ] - Herons Theorem does the same thing differently.
Area of Base triangle bounded by | a, b, c |
Aabc=
xyz | |
2htet |
Aabc=
\sqrt{x2y2+z2l[x2+y2r] | |
}{2} |
Area of all 4 surfaces of a Tri-Rectangular Tetrahedron
Aabc=
xyz | |
2htet |
Axy=
xy | |
2 |
Axz=
xz | |
2 |
Ayz=
yz | |
2 |
Total area of a Tri-Rectangular Tetrahedron
Atet=
xy+zl[x+yr]+\sqrt{x2y2+z2l[x2+y2r] | |
}{2} |
a=14.4 b=10 c=12
x=9.037698822156002781875821128798
y=11.210709165793214885544254958172
z=4.2801869118065393196504607419769
The old way. Pythagorean's Theorem TWO dimensional. Then Modified for 3 dimensions BUT ONLY for Tri-Rectangular Tetrahedrons.
Givenl[x,y,zr] a=\sqrt{ x2+y2 } b=\sqrt{ x2+z2 } c=\sqrt{ y2+z2 }
Given l[a,b,cr] x=\sqrt{ | a2+b2-c2 | } y=\sqrt{ |
2 |
a2+c2-b2 | } z=\sqrt{ | |
2 |
b2+c2-a2 | |
2 |
}
See main article: De Gua's theorem. If the area of the base is
T0
T1
T2
T3
2. | |
T | |
3 |
This is a generalization of the Pythagorean theorem to a tetrahedron.
The area of the base (a,b,c) is always (Gua) an irrational number. Thus a trirectangular tetrahedron with integer edges is never a perfect body. The trirectangular bipyramid (6 faces, 9 edges, 5 vertices) built from these trirectangular tetrahedrons and the related left-handed ones connected on their bases have rational edges, faces and volume, but the inner space-diagonal between the two trirectangular vertices is still irrational. The later one is the double of the altitude of the trirectangular tetrahedron and a rational part of the (proved)[3] irrational space-diagonal of the related Euler-brick (bc, ca, ab).
Trirectangular tetrahedrons with integer legs
a,b,c
d=\sqrt{b2+c2},e=\sqrt{a2+c2},f=\sqrt{a2+b2}
a=240,b=117,c=44,d=125,e=244,f=267
Trirectangular tetrahedrons with integer faces
Tc,Ta,Tb,T0
a=42,b=28,c=14,Tc=588,Ta=196,Tb=294,T0=686,h=12
a=156,b=80,c=65,Tc=6240,Ta=2600,Tb=5070,T0=8450,h=48
a,b,c