Analytic geometry and principles of algebra (1913)
Ziwet, Alexander, 1853-1928, Hopkins, Louis Allen, joint author, Hedrick, E. R. (Earle Raymond), 1876-1943 · New York, The Macmillan Company · leaf 184
of 7^ from the directrix is2 a + r cos cf>, so that the polar equation is now (2) r=-^^^. We have assumed a as a positive number, 2 a denoting theabsolute value of the distance between the fixed point (focus)and the fixed line (directrix). The radius vector r is thenalways positive. But the… … 174. Mechanical Construction. A mechanism for tracingan arc of a parabohi consists uf a right-angled triangle (shaded in Fig. 65), one ofwhose sides is applied to the directrix.At a point R of the other side BQ ^string of length i?Q is attached ; the otherend of the string is attached at the…
Geometry, Analytic
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