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 272
277. Prove that if any point outside a circle be joined tothe vertices of any circumscribed quadrilateral, and two tan-gents drawn from the point, these six lines form a pencil ininvolution. … 244* EXERCISES ON EUCLID [278. I will prove this theorem, by shewing that it is the polarreciprocal of (213). Let P be the point outside the circle, and LMNR the quadri-lateral touching the circle at the points I, m, n, r. Draw thetwo tangents PB, PB. Then shall PM, PB, PL, PN, PB, PRform a pencil…
Geometry
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