Schmall, Charles Nelson. [from old catalog] · New York, D. Van Nostrand company · leaf 328
SURFACES OF REVOLUTION 311 … Fig. 172. The Graph of the equations, b cos 2 n-a i = ± b sin 2 7T~] for two values of b, repcesentingthe plan of the spirals of a doublethreaded screw of pitch a.
Geometry, Analytic
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