An elementary treatise on coordinate geometry of three dimensions (1912)
Bell, Robert J. T. (Robert John Tainsh), 1877-1963 · London : Macmillan and co., limited · leaf 397
nd therefore _w -qm,+ n.. cos (0 = J. - * ^=—- (II The binomial makes an angle 90° + ^ with the normal tothe surface. Let us take as the positive direction of thebinomial that which makes an angle 90° — w with the normalto the surface, and then choose the positive direction of the 374 COORDINATE… … Fig. 70. Differentiate with respect to st the arc of the curve, andwe have, by (1), dco cos to thirty + smx) + mz{slx + tmx) cos to ds s/l-\-p2 + q2 d -* •(2) Now take O as the origin, and let the equation to thesurface be 2: :- + £+.... Pi P-2 Then at the origin (2) becomes doe cos to l.X rti^ni,…
Geometry, Analytic
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