Smart, Edward Howard · London : Macmillian and Co. · leaf 164
f a Hyperbola andits Pseudo-conjugate. {a) It follows at once from the above, that the area of theparallelogram in IV, is constant. For it is obviously four times that of the triangle LCL. 136 PROJECTIVE GEOMETRY (b) The difference of the squares of these diameters isconstant. For (Fig. 72) PD… … Fig. 72. This constant is evidently a^ - b^, as is seen by taking Pand D at A and B respectively. Corresponding properties hold for the ellipse, but are bestestablished by separate treatment, as in the following articles. § 7. The Ellipse can always be obtained as the Or-thogonal Projection of a…
Geometry, Projective
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