Plane and solid analytic geometry; an elementary textbook (1905)
Ashton, Charles H. (Charles Hamilton), 1866- · New York, C. Scribner's Sons · leaf 233
0, 2/ = P sin <|) sill 0, [8] z = p cos <|>. Note. — Spherical coordinates have usually been called polar coordi-nates. But the application of the system described in Art. (5 is morenearly analogous to the uses of polar coordinates in two dimensions. 8. Angle between two lines. — Let a^,… … Fig. 7. Then by [1] or by [6] = (/Oi cos a^ - p^ cos a^y + (p^ cos ^j - p^ cos fi^y + (PiCOsyi-p^cosy^y, or by [7] = Pi^-^p2 - 2 P1P2 (cos a^ cosa^-\- cos ff^ cos ^^ + cos 7i cos 72). Ch. I, § 8] COOKDINATE SYSTEMS. THE TOINT 217 But by the law of the cosines Hence cos 0 = cos ai cos a^ + cos Pi…
Geometry, Analytic
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