Fig 10 1
© NCERT
not to be republished
 MATHEMATICS
426
A
O
P
90°
X
Y
Z
X
A
O
B
P(
)
x,y,z
C
P(
x,y,z)
r
x
y
z
Direction Cosines
Consider the position vector 
OP or 
uuur
rr  of a point P(x, y, z) as in Fig 10 3 The angles α,
β, γ made by the vector rr  with the positive directions of x, y and z-axes respectively,
are called its direction angles