Practical plane and solid geometry for advanced students, including graphic statics, adapted to the requirements of the South Kensington syllabus (1899)
Harrison, Joseph, Baxandall, George Albert · London Macmillan · leaf 116
hich bisects any system of parallelchords is called a diameter, and is parallel to the axis, whichis a particular diameter. Theorem 8.—The line TN, through T,parallel to the axis,bisects the chord PQ, and TN is bisected at A. That is, PN= NQ, and TA = AN Theorem 9.—The tangent XY at A is parallel… … 101. Problem.—To draw the tangent and normalto a given parabola at a given point P on the curve. (See the upper figure.) Join P to the focus F, and drawPM parallel to the axis; bisect the angle PPM by theline PP. Then PP is the tangent at P. Or, make PP= PP and join PP. Or, make AP=AJV and join PP.…
![An illustration from L'optique divisée en trois livres : ou, l'On démontre d'une maniere aisée tout ce qui regarde 1. la propagation & les proprietez de la lumiere. 2. La vision. 3. La figure & la disposition des verres qui servent à la perfefectionner [sic] (1682)](https://img.insideoutlibrary.com/img/200/ia-loptiquedivise00ango-79-9.webp)
