Smart, Edward Howard · London : Macmillian and Co. · leaf 73
. 17. It is a good exercise in the application of the principle ofcontinuity to deduce from this the result of § 5. § 7. Prop. If two curves cutone another, their inverses cut atthe same angle. Consider first a single curve andits inverse. Take two near positions of theradius vector, and let P, P,… … 46 PROJECTIVE GEOMETRY ultimate coincidence, P, Q on the inverse curve will dothe same, and PQ, PQ become finally the tangents to thegiven curve and its inverse at the points P, P respectively.So that the tangents at P to the original curve and at P tothe inverse curve make equal angles with the…
Geometry, Projective
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