Elements of analytical geometry and of the differential and integral calculus (1866)
Davies, Charles, 1798-1876 · New York, Barnes & Co. · leaf 175
es, viz.: • x =z r cos JT, y = r cos rj 2 = r cos Z, By squaring these equations, and adding, we obtain, rf.fn 4_ y2 4. ^2 _ r2(cos-X + cos2 T -f cos^Z). But we have already found, Hence, cos^X-f cos^F-f cos^Z = 1; that LS, the sum of the squares of the cosines of the threeangles which a straight… … the co-ordinate plane ZX, and CP, its projection onthe co-ordinate plane YZ.Since CP is the pro-jection of the line on theco-ordinate plane ZX, theline itself, in space, is inthe plane passing throughC P, and perpendicularto the co-ordinate plane,ZX (Art. 9). Since CP is the projection of the line…
Geometry, Analytic · Calculus
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