An elementary treatise on analytical geometry : embracing plane co-ordinate geometry, and an introduction to geometry of three dimensions (1869)
Johnson, William Woolsey, 1841-1927 · Philadelphia : J.B. Lippincott · leaf 115
%n2p, which is the negativeof the value of Xx the ab-scissa of Pj j that is, YT =Y.R and is measured in theopposite direction. HenceTR, which is called the sub-tangent, is bisected at thevertex. The line PXN, drawn per-pendicular to the tangent at the point of contact, is called a normal; and the… … OBLIQUE CO-ORDINATES OF PARABOLA. Ill Therefore RN = p, or the subnormal is constant and equals halfthe parameter. 150. Since VF = %p, TF == Xa -f ip = \ TN, hence a perpen-dicular FB to the tangent bisects TPX by the similar trianglesTFB, TNPj. But the axis of Y also bisects TP1} and thereforecuts…
Geometry, Analytic
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