Smith, David Eugene, 1860-1944 · Boston, New York [etc.] Ginn and Company · leaf 335
324 THE TEACHING OF GEOMETRY tangents to two circles. If the figure be revolved aboutthe line of centers, the circles generate spheres and thetangents generate conical suriaces. To study this casefor various sizes and positions of the two spheres is oneof the most interesting generalizations of… … is on the other side of the earth. In this case the part MIX isfully illuminated by the moon, but the zone ABNM is only partlyilluminated, as the figure shows.1 Theorem. The sum of the sides of a spherical poly-gon is less than 360°. In all such cases the relation to the polyhedral angleshould be…
Geometry
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