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 66
O, Fig. 38, be thegiven points, and F the given focus. Connect thepoints with the focus, and draw O N, and N M,and produce them towards the probable positionof the directrix, as to L and K. Now, take apoint R, on QL, such that OF : N F : : OR :NR,* and R is a point in the directrix. In likemanner,… … EiG. 38. OP, NQ, and MX, NQ M being perpendicular to AB. Now OP: NQ ::OR : NR. But by construc- O^F _ N^p6 ~NF ton OR:NR::OF:NF. In like manner NQ : M .-. OP : OF :: NQ : NF, orN S : M S : : N F : M F. NQMF NQ MT Q. E. D. To make the numerical computations requires much more labor than to effectthe…
Geometry, Analytic · Calculus
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