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 130
olars. Ex. 6. Prove: The portion of a movable tangent of a centralconic between the two tangents at the vertices subtends right anglesat the foci. Ex. 7. The lines joining the points of intersection of all circlesthrough the foci with the tangents at the vertices of a central conicare the tangents… … Fig. 48. at C. Then PF is the polar of C. Consequently FAPBC isa harmonic pencil in which one pair, FP, FC is perpendicular.FP therefore bisects the angle AFB, § 5. Hence the proposi-tion: The line joining a focus to the point of intersection of two tan- Il8 PROJECTIVE GEOMETRY. gents of a conic…
Geometry, Projective · Geometry, Analytic
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