Write the direction-cosines of the line joining the points (1, 0, 0) and (0, 1, 1). [CBSE 2011]

Assuming the points to be P and Q.

The line joining the points P(1,0,0) and Q(0,1,1) can be represented with a vector . the given points P and Q can be represented using position vectors

As

∴

We know that direction cosine of a vector is given as-

cos α = ; cos β = and cos γ =

∴ Direction cosine of or line joining the points (1, 0, 0) and (0, 1, 1) is –

cos α =

cos β =

and cos γ =