An introduction to projective geometry and its applications; an analytic and synthetic treatment (1905)
Emch, Arnold, b. 1871 · New York, J. Wiley & sons; London, Chapman & Hall, limited · leaf 29
/sin (ad) CN /DM sin (ac) /sin (ad)(l) sin (be)/ sin (bd)= /sin (ad) CJy //sin (bd)~~CP/ sin (be)/ sin (bd) CP I DO DM and CN being _L a and DO and CP _L to b. But CN AC J CP BC , DM=AD and DO=BD] henCC CN /DM AC /ADCP / DO~ Bel BD (2) (abed) = (A BCD). i6 PROJECTIVE GEOMETRY. This important result… … Fig. 7. In other words, if the rays a, b, c, d are considered as project-ing rays in a central projection, such a projection does not changethe anharmonic ratio of four points. A system of rays in a plane and passing through the samepoint is called a pencil of rays.1 By the above theorem all…
Geometry, Projective · Geometry, Analytic
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