Godfrey, C. (Charles), 1873-1924, Siddons, A. W. (Arthur Warry) joint author · Cambridge, University Press · leaf 148
? … Cross-ratio of a pencil of parallel lines. If the vertex of a pencil retreats to infinity, the rays becomeparallel, and the angles of the pencil become zero. By theprinciple of continuity, we may be assured that all transversalsstill cut the pencil in equicross ranges; this property is,…
Geometry, Modern
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