Beman, Wooster Woodruff, 1850-1922, Smith, David Eugene, 1860-1944 · Boston, Ginn & company · leaf 351
For by step 7 they have the same center, P, and the same radius. 2. The perpendiculars to the four faces of a tetrahedron,through the circumcenters of those faces, are concurrent. For each of these perpendiculars passes through P, the center of thesphere whose surface is determined by the four… … E.g. the angle made by arcs AP, BP is defined as the planeangle APB. 458. From this definition follow these corollaries : 1. The angle made by two arcs has the same numericalmeasure as the dihedral angle of their planes. (§ 359.) 2. An angle made by tivo arcs has the same numerical meas-ure as the…
Geometry
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