TRISECTRIX, a curve which is a variety of the limacon (q.v.) of Pascal, and named from its property of trisecting an angle. The polar equation is r=i + 2 cos 6 and the form of the curve is shown in the figure. To trisect an angle by means of this curve, o v describe a circle with centre O and radius OE, and let the given angle which is to be trisected be laid off from OE and cut the circle at S; let the chord ES cut the trisectrix in J. Then OJ trisects the given angle.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)