Osgood, William F. (William Fogg), 1864-1943, Graustein, William C. (William Caspar), 1888-1941, joint author · New York : The Macmillan Company · leaf 573
Fig. 6 554 ANALYTIC GEOMETRY It is never a surface of revolution, no matter what values areassigned to a and b. The sections of the surface by the vertical coordinate planesare the parabolas x = 2u% » y^ = -2b% of which the first opens upwards and the second, downwards. The section by the (x,… … OA: OB: X + 1 = 0, a 0 X a b Fig. 7 A section parallel to and abovethe (x, 2/)-plane is a hyperbolawhose vertices are on the parabolaopening upwards, whereas a sec-tion parallel to and below the (x, 2/)-plane is a hyperbolawhose vertices are on the parabola opening downwards. It isseen, then, that…
