Smart, Edward Howard · London : Macmillian and Co. · leaf 205
on the directrix. Ex. From properties of the parabola prove (assuming that only oneparabola can be drawn to touch four given straight lines) that (1) the circumcircles of the four triangles formed by four given straight lines are concurrent; (2) the orthocentres of these triangles are collinear. §… … Fio. 94. Then PQ, P^ measure the deflections of the curves from thetangent line (Fig. 94). P.O. M 178 PROJECTIVE GEOMETRY PQConsider the ratio —-^. If it were unity for all positions of P near A, the curves would coincide in that neighbourhood, and their curvatures would be the same. We shall…
Geometry, Projective
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.
