Which one of the following relations among the direction cosines of any vector is…

MATHEMATICS · Single correct · CBSE · Mathematics · Three-Dimensional Geometry · Three-Dimensional Geometry

Problem

Which one of the following relations among the direction cosines

l,\,m,\,n

of any vector is always true? (a)

l^{2}+m^{2}-n^{2}=1

(b)

l+m+n=1

(c)

l^{2}+m^{2}+n^{2}=1

(d)

lm+mn+nl=1