An elementary treatise on modern pure geometry (1893)
Lachlan, Robert · London, New York, Macmillan and Co. · leaf 50
he two harmmiic ranges ondifferent straight lines, then the lines BB, PP, QQ will he con-current and the lines BB, PQ, PQ will he concurrent. Oh … Let PP, BB intersect in 0, and join OA, OQ. Then since0 [AB, PQ} is a harmonic pencil, the line AB will be dividedharmonically by OP, OQ. But OP cuts AF in P. Hence OQmust cut AB in Q the point which is conjugate to P withrespect to A, B. Again, let PQ cut BB in 0, and join OA, OP. Then thepencil 0…
Geometry
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