Young, George, jr, Baxter, Hubert Eugene, joint author · New York, The Macmillan Co. · leaf 269
ght Line on a CurvedSurface. I. First Method. The umbra of a straight line is a plane.This plane will cut the given surface in a curved line, which isthe required shadow. If the source of light is a given point, pass a plane throughthe point and the given line, as in § 69, and find the… … Fig. 235 XII, § 214] SHADES AND SHADOWS 253 II. Second Method. The method given here is analogousto the slicing method of § 149, and furnishes the basis for thesolution of the following two problems. Let the hemisphere and the line ah, Fig. 236, be given, andlet it be required to find the sun…
Geometry, Descriptive
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