Osgood, William F. (William Fogg), 1864-1943, Graustein, William C. (William Caspar), 1888-1941, joint author · New York : The Macmillan Company · leaf 325
s the circle is seen to be carried into an ellipse. It remains to prove that the lines D and D, into which two conjugate diameters D and D of the circle are carried by the compression, are conjugate diameters of the ellipse. If the angle <^ is as shown in Fig. 14, the slopes of D and D are tan… … Fig. 15 Consequently, D and D, according to Th. 3, § 2, are conjugate diameters of the ellipse, q. e. d. If the center 0 of the circle lies on the central line (Fig. 15), the circle is the auxiliary circle of the ellipse (Ch. VII, 10), and the angle <^ is the eccentricangle for the extremity P…
