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Diagram used to prove the theorem: "Two trihedral angles, which have three face angles of the one equal respectively to three face angles of the other , are either equal or symmetrical."

Symmetrical or Equal Trihedral Angles

Diagram used to prove the theorem: "Two trihedral angles, which have three face angles of the one equal…

Illustration showing two prisms are equal if the three faces which include a trihedral angle of the one are respectively equal to three faces which include a trihedral angle of the other, and are similarly placed.

Equal Prisms

Illustration showing two prisms are equal if the three faces which include a trihedral angle of the…

Diagram used to prove the theorem: "The sum of two face angles of a trihedral angle is greater than the third."

Face Angles of Trihedral Angle

Diagram used to prove the theorem: "The sum of two face angles of a trihedral angle is greater than…