An elementary treatise on modern pure geometry (1893)
Lachlan, Robert · London, New York, Macmillan and Co. · leaf 142
intersection of two diagonals of a tetra-gram lines are drawn respectively parallel to the four sides and intersectingrespectively the sides opposite to those to which they are parallel. Provethat these four points of intersection lie on a straight line. [Triu. Coll., 1890.] Let A, A; B, B; C, C be… … with the figure BCBC If OA be drawn parallel to BC to meet BC in X,and if OA be drawn parallel to BC to meet BC in A, it is evident that XXwill be that line of the figure BCBC which corresponds to the line at infinityin the figure BCBC. Hence the theorem is proved.It may be noticed that XX is…
Geometry
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