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 175
ire revolution; but it describes theright branch by negative values, and the left by positive. 230. The first value of r, which is positive for the branch withinwhich the focus is situated, might have been derived from the valueof r, in Art. 221. Now x in r = ex — A denotes the abscissa CRmeasured… … This is the same relation as that shown in Art. 184 to exist be-tween the radius vector andabscissa of the ellipse as re-ferred to its focus; it is equi-valent to the first value of r,and applies to all conic sec-tions.* In the hyperbola, the valueof r thus found is positivefor the right branch,…
Geometry, Analytic
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