Analytic geometry and principles of algebra (1913)
Ziwet, Alexander, 1853-1928, Hopkins, Louis Allen, joint author, Hedrick, E. R. (Earle Raymond), 1876-1943 · New York, The Macmillan Company · leaf 297
can also be written in the form I Vi — 111 _ ^2 —m n 1 _ d. f[2,m,.7j^ 299. Angle between two Lines. If the directions of two linesare given by their direction cosines l^, m^, n^ and lo, nu, n^, theangle xj/ between the two lines is givenby the formula cos xj/ = lih + rni7n2 + riin^- ^For, drawing… … XIII, § 301] COORDINATES 285 cosine of the required angle i}/. On the other hand, OP^ hasli, iRi, /*! as components along the axes; hence, by § 294: cos ij/ = IJ2 + iiih -\- >i>^2-Two intersecting lines (or any two parallels to them) maketwo angles, say xp and tt — ip. I)iit if the direction…
Geometry, Analytic
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