Projective geometry for use in colleges and schools (1911)
Milne, William P. (William Proctor), 1881- · London : Macmillan · leaf 136
e four given lines touched by eachof the members of a four-line system of conies. Let the line joining pq, rs be apr, sq be bps, qr be c. Project pg and rs into the Circular Points at Infinity. We thus get a system of con focal conies having astheir four foci the points pV, ps, qr, qs (Chap.… … Any other circle of the system cuts the line in two pointsthat harmonically separate the points of contact.^^^^ 116 PROJECTIVE GEOMETKY This is plain since OX- = OH . OK,OY- = OH.OK,OP.OQ=-OH.OK;.-. OX- = OY- = OP.OQ.Hence [PXQY] is harmonic. We can now generalise this Theorem by projectionand…
Geometry, Projective
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