Dowling, L. Wayland (Linnaeus Wayland), b. 1867, Turneaure, F. E. (Frederick Eugene), 1866- · New York, H. Holt and company · leaf 217
d direction cosines of a directed segment. The angles which a directed segment makes with the positivedirections of the coordinate axes are called the direction angles ofthe segment. The cosines of the direction angles are called the direction cosines of the segment.Through Pi draAV lines paral-lel… … ^X COS « = I COS /3 _ ^2 - yi Fig. 120 COS y 147. Relation connecting the direction cosines of a segment.Theorem. The sum of the squares of the direction cosines of anysegment is equal to unity. Arts. 146, 147] RELATION CONNECTING COSINES 201 For let I be the length of any segment. Then (Art. 145),…
Geometry, Analytic
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