Newcomb, Simon, 1835-1909 · New York, H. Holt and company · leaf 207
dstraight line NR and any fixed point F,and against the former fasten a ruler,and place another ruler, right-angled atN, so that its edge, NH, may move freelyalong NR. At F attach one end of athread equal in length to the hypothe-nuse HQ of the ruler, and the other endto the extremity Q of the… … and therefore = a constant. PF= PR; PF _ PRPI)~ PD _m NQ 181. Cor. From §§ 97, 148 and 180 it follows that wemay define a conic section as the locus of a point which movesin such a way that its distance from a fixed point (the focus)is in a constant ratio to its distance from a fixed straightline…
Geometry, Analytic
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