Osgood, William F. (William Fogg), 1864-1943, Graustein, William C. (William Caspar), 1888-1941, joint author · New York : The Macmillan Company · leaf 219
becomes negative, so thatthere are no points on thecurve. This situation persiststhroughout the angle 30° < (9 < 90°. In the angle 90° < ^ < 150°, however, r is again positive. The piece of the curve which lies in this angle is congruent to the pieceOA already plotted and may be… … Fig. 12
