Newton's Principia, sections I, II, III, with notes and illustrations. Also a collection of problems (1863)
Newton, Isaac, Sir, 1642-1727, Frost, Percival, 1817-1898 · Cambridge, London, Macmillan and Co · leaf 84
38. In the construction for this Lemma, BD must be a subtense, i. e. inclined throughout the change of position at a finiteangle to the tangent or chord, for, otherwise, the angles BADand ABD being both small, the ultimate ratio of the chord tothe tangent might be any finite ratio instead of being… … Here b, d are the distant points, that is, points at a finitedistance from A; BD, J?D, BD are consecutive positions ofthe subtense, when B approaches towards A, and db, db, db areparallel to these, Acb, Acb are the forms of Acb changed so asto be always similar to the corresponding portion of A CB…
Mechanics · Celestial mechanics
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