. Memoirs and proceedings of the Manchester Literary & Philosophical Society. Fig. 14. Method of Jordanus. 22 Gee AND ADAMSON, Trisecting an Angle. drawing BH perpendicular to BC and placing a straightline AKE through A so that the intercept KE is equal tothe radius of the circle. BG, drawn parallel to AKE isthen a trisector. (Compare with Figs. I and 5.) Thismethod is given by a monk, Jordanus Heaccomplished the trisection by giving a ruler simul-taneously a rotating and sliding motion, its final positionbeing fixed with the aid of a certain length marked onthe III. Als
. Memoirs and proceedings of the Manchester Literary & Philosophical Society. Fig. 14. Method of Jordanus. 22 Gee AND ADAMSON, Trisecting an Angle. drawing BH perpendicular to BC and placing a straightline AKE through A so that the intercept KE is equal tothe radius of the circle. BG, drawn parallel to AKE isthen a trisector. (Compare with Figs. I and 5.) Thismethod is given by a monk, Jordanus Heaccomplished the trisection by giving a ruler simul-taneously a rotating and sliding motion, its final positionbeing fixed with the aid of a certain length marked onthe III. Alsidschzi12 used the following method: Let ABCbe the angle {Fig. 15) to be trisected. With B as centre. Fig. 15. Method of Alsidschzi. and any radius BA describe a circle. Through A place a 10 De Triangulis {circa 1170), printed by Curtze in 1887. 11 See Cantor, Vorlesungen iiber Geschichte der Mathematik, Vol. II.,p. 75, 1892. 1 - An Arabian mathematician. Manchester Memoirs; Vol. lix. (1915), No. 13. 23 straight line ADE so that the intercept DE shall be equalto DB. Join ZsZ> and produce EB to /*. Then obviouslythe angle CBF is one-third of the angle ABC. IV. The following two methods are given by G. von Lowenthurn in the course of a correspondencewith Huygens (1653-4)15:
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