Hawkins electrical guide ... : questions, answers & illustrations : a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications ; a practical treatise (1914)
Hawkins, N. (Nehemiah), 1833-1928 · New York : T. Audel & Co. · leaf 37
f the two faces is the same, which is the usual condition, by observing that thetriangles CO A and COA are equal, and therefore that OC = OC, which gives the pointO. If the curvatures be unequal, the triangles COA and COA are similar, and either COor CO may be found, and therefore also the point O.… … Fig 3 797 —Secondary axis. This is any right line passing through the optical center, but not through the centers of curvature. Rays emitted from a point P on the secondary axis PP nearly converge to a center point P on the axis PP, and according as the distance from the ooint P to the lens is…
Electrical engineering
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