Plane and solid analytic geometry; an elementary textbook (1901)
Ashton, Charles H. (Charles Hamilton), 1866- · New York, C. Scribner's sons · leaf 127
ne DH has been called the directrix, and thepoint Ff the focus. Place the points F and D on theX-axis so that CF= FQ and CD = DfC, and draw DHperpendicular to the X-axis. The symmetry of the curve 108 ANALYTIC GEOMETRY [Ch. IX, § G5 shows that if we had used the line DH and the point F asdirectrix… … We can now obtain the relations between the variouslines in the figure. We have seen that FD = DF = m, OD = = BC = m 1 -e2 CA-- = A0 = a em 1-e2 nn - - wr? l em It follows that CD = -, and that the equations of thedirectrices are x = % and sc = -^Le e [38] Ch. IX, § 65) CONIC SECTIONS 109 Also that…
Geometry, Analytic
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