Analytic geometry and principles of algebra (1913)
Ziwet, Alexander, 1853-1928, Hopkins, Louis Allen, joint author, Hedrick, E. R. (Earle Raymond), 1876-1943 · New York, The Macmillan Company · leaf 198
this tangent at the vertex. The propertiesjust proved that tlie tangent at P bisects the angle between thefocal radius PF and the parallel PD to the axis and that theperpendicular from the focus to the tangent meets the tangent onthe tangent at the vertex are of particular importance. 193.… … Similarly, in a parabola, the locus of the midpoints of all chordsparallel to any given direction is a straight line, and this linewhich is parallel to the axisis called a diameter of theparabola. To prove this, takethe vertex as origin and theaxis of the parabola as axis Ox(Fig. .72) so that the…
Geometry, Analytic
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