Osgood, William F. (William Fogg), 1864-1943, Graustein, William C. (William Caspar), 1888-1941, joint author · New York : The Macmillan Company · leaf 32
AVhen L rotates as shown inthe figure, X becomes positive and increases steadily in value.As L approaches the vertical line L, X becomes very large,increasing without limit. When L passes beyond L, X changes sign, being still nu-merically large. As L continues to rotate, X increases alge-braically… … Fig. 6 When L is in the position of L, 0 is 90° and tan ^ = X isundefined, that is, has no value. Hence V has no slope. Oneoften sees the expression : tan 90° = oo, and, in accordance withit, one might write here, A = go. This does not mean that IJ hasa slope, which is infinite, for infinity is not…
