An elementary treatise on modern pure geometry (1893)
Lachlan, Robert · London, New York, Macmillan and Co. · leaf 105
It follows that the lines xx, yy\ zi are concurrent, and that if 0 be thepoint in which they intersect, each segment such as xx is divided harmonicallyin the point 0 and the point where it cuts the line XX. Ex. Deduce the theorem given in § 140, Ex. 1, by considering the lineXX to be the line at… … OF A TETRASTIGM. 89 Let ABGD be any tetrastigm, and let any straight line cut theconnectors BD, AG in P, P; the connectors CD, AB in Q,Q; andthe connectors BG, AD in R, R. Then the range [PP, QQ, RR}will be in involution. Since the line BD cuts the sides of the triangle AQR in thepoints P, D, B, we…
Geometry
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