Dowling, L. Wayland (Linnaeus Wayland), b. 1867, Turneaure, F. E. (Frederick Eugene), 1866- · New York, H. Holt and company · leaf 139
to the X-axis. The equation of the tangentto the parabola at the pointP(x„ y,) (Fig. 75) is (Art. 97) Hence, the tangent meetsthe X-axis at the pointT = ( - x„ 0). Therefore TO= OD, and, if EG is thedirectrix and F the focus,E0= OF. Hence, TF =ED. But ED = FP (defi-nition of the parabola),… … Fig. 75 EXERCISES 1. Two parabolas have a common axis and a common focus, and extendin opposite directions. Show that tliey intersect at right angles. 2. Given the focus and the vertex of a parabola, but not tlie constructedcurve, show how to draw the two tangents through a given point P.…
Geometry, Analytic
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