Plane and solid analytic geometry; an elementary textbook (1904)
Ashton, Charles Hamilton, 1866-1936 · New York, C. Scribner's Sons · leaf 125
ine DlP 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 = DC, and draw DRperpendicular to the X-axis. The symmetry of the curve 108 ANALYTIC GEOMETRY [Ch. IX, § 65 shows that if we had used the line BH and the point F asdirectrix… … We can now obtain the relations between the variouslines in the figure. We have seen that FB = DF = m,CB = BC = 1-e5 CA = AC =a em CB = B0 =b = em VI It follows that CB = ~, and that the equations of thedirectrices are v = % and x=-^. [38] e e Ch. IX, § 66) CONIC SK(TI()XS 1U(.) Also that CF=CD-FI)…
Geometry, Analytic
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