Osgood, William F. (William Fogg), 1864-1943, Graustein, William C. (William Caspar), 1888-1941, joint author · New York : The Macmillan Company · leaf 444
^y DIRECTION COSINES 425 … Fig. 4 Lgle between Two Directed Lines. Let it be required tollie angle Q between the two directed lines, L^ and Z2,whose direction angles are «!, ySi, yiand ttg, /82, 72- We can assume without loss ofgenerality that L^ and L^ passthrough the origin.^ Take anypoint P: (ao, ?/o, ^o) o^ ^i? so that…
