Girish Mahajan (Editor)

Trirectangular tetrahedron

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Trirectangular tetrahedron

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.

Contents

Metric formulas

If the legs have lengths a, b, c, then the trirectangular tetrahedron has the volume

V = a b c 6 .

The altitude h satisfies

1 h 2 = 1 a 2 + 1 b 2 + 1 c 2 .

The area T 0 of the base is given by

T 0 = a b c 2 h .

De Gua's theorem

If the area of the base is T 0 and the areas of the three other (right-angled) faces are T 1 , T 2 and T 3 , then

T 0 2 = T 1 2 + T 2 2 + T 3 2 .

This is a generalization of the Pythagorean theorem to a tetrahedron.

References

Trirectangular tetrahedron Wikipedia