An introduction to projective geometry and its applications; an analytic and synthetic treatment (1905)
Emch, Arnold, b. 1871 · New York, J. Wiley & sons; London, Chapman & Hall, limited · leaf 54
ance B, on the polar of A, it isclear that the polar of B must pass through A, since A is har-monic to B with regard to C and D as the other pair. Thusthe theorem: The polar of a point which is situated on the polar of anotherpoint passes through the latter point. Conversely, the pole ofa straight… … Fig. 15. the pole of the ray (ABCD), through A. Using the results of§ 8, concerning the complete quadrilateral, it is now easy to givea simple construction of the polar of a point, or of the pole of astraight line. Through A draw any two rays intersecting the 42 PROJECTIVE GEOMETRY. circle in the…
Geometry, Projective · Geometry, Analytic
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