Smart, Edward Howard · London : Macmillian and Co. · leaf 182
essed in the loop soas to keep the two portions SP, SP always taut will trace outon the plane an ellipse having S, S as foci, and major axisequal to the length of the thread. Hyperbola. One end of a long straight rod SL is fixed atS, so that the rod is free to turn about it in a plane. A thread SPL… … trace out on the plane a portion of an hyperbola. To get theother branch, fix the end of the rod at S and fasten the stringat S (Fig. 79). Parabola. Take a straight bar RK, bent rigidly at rightangles for a short length KL. A string of length RK has oneend fastened to R and the other to a fixed…
Geometry, Projective
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