Exercises on Euclid and in modern geometry for the use of schools, private students, and junior university students (1881)
McDowell, James L · Cambridge, Deighton, Bell, and Co. · leaf 245
encil thus formed has its angles respectively equal to theangles of the pencil formed by the four polars (244). Thereforethe anharmonic ratio of four points in a straight line is equal tothat of their polars. Q. e. d. 246. If three pairs of tangents he drawn to a circlefrom three points in a… … Since the chords of contact AA\ BB, and CG are the polarsof three points D, E, F in a straight line, therefore (240) theypass through P the pole of DF. Now, if a seventh tangent cutthe six tangents, the anharmonic ratio of any four points of inter-section is equal to that of the four points of…
Geometry
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