Schmall, Charles Nelson. [from old catalog] · New York, D. Van Nostrand company · leaf 158
bola from two points onthe axis equidistant from focus, the difference of their squares will beconstant. If P^, Pg, are the points, the product = 2 a • PjPg. 20. The tangent at one extremity of a focal chord is parallel to thenormal at the other extremity. Suggestion. —Let (x^, i/,), (.To, 7/2), be… … Fig. 109. (1) The subtangent is bisected at the vertex. In put 2/ = 0. .-. x = -Xi, i.e., ON = OT. (2) The subnormal is constant and equal to the semilatusrectum 2 a. In the equation of the normal, viz., put y = ^ We get X — x^ — 2a, or NN = 2 a. Hence, etc. (3) FP = FT, for FP = CN = ON + a = OT +…
Geometry, Analytic
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