A general geometry and calculus : including book I. of the general geometry, treating of loci in a plane; and an elementary course in the differential and integral calculus (1881)
Olney, Edward, 1827-1887 · New York : Sheldon and Co. · leaf 215
s at B, fasten the other end of the string at one focus, as at F, andthe other end of the ruler at the other focus, as at F. Place a pencilagainst the string and bear it against the side of the ruler, as at P, andkeeping the string tense move the pencil around the curve. It is evidentthat FP — PF =… … Fia. 196. 203, JPtop*—The radii vectores drawn to any point in an ellipse ofhyperbola make equal angles with the tangent at that point. Dem.—Let PF and PF, be the radiivectores, and M T the tangent, Figs. 195,197. ThenFPT=F PM. For,AT = — {137, Bx. 1, ox 276, Ex. 4), and AF =:A F==Ae. Hence, in the…
Geometry, Analytic · Calculus
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