Question

Define direction cosine of a line. If l,m,n are direction cosines prove that

Answer 1

 Direction cosines of a line are the cosines of the angles made by theline with positive directions of the co-ordinate axes. 11.1.2 If l, m, n are thedirection cosines of a line, then l2 + m2 + n2 = 1. 11.1.3 Direction cosinesof a line joining two points P (x. 1. , y.