Thus, the coordinates of the point P may
also be expressed as (lr, mr,nr) The numbers lr, mr and nr, proportional to the direction
cosines are called as direction ratios of vector rr , and denoted as a, b and c, respectively Fig 10 2
© NCERT
not to be republished
VECTOR ALGEBRA
427
�Note   One may note that l2 + m2 + n2 = 1 but a2 + b2 + c2 ≠ 1, in general