Young, George, jr, Baxter, Hubert Eugene, joint author · New York, The Macmillan Co. · leaf 138
es and surfaces, since the classifications are consistently based on thesame conception and are made to depend on geometric relations that areeasily visualized. VII, § 108] CURVED LINES 121 so produced is tangent^ to the curve. Such a Hne evidentlycontains two consecutive points of the curve and… … Fig. 118 (to touch), which expresses quite closely the fundamental ideainvolved. Any line perpendicular to a tangent, at the point of tangency,is said to be normal to the curve. 108. Classification. I. Regular and Freehand Curves. When the generat-ing point of any curve changes its direction in…
Geometry, Descriptive
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