Three Dimensional Geometry

Here ...(1)
is given straight line
Let P = (1, - 1, 0) on the straight line.
Here direction ratios of line (1) are (2, - 3,1)
direction cosines of line (1) are

Equation of line (1) may be written as
....(2)

Co-ordinates of any point on line (2) may be taken as

Let Q =
Given
Putting the value of , we get
Q = and Q

Given,


and
Eqs. and , can be written as

and

Since, both are perpendicular to each other, then

Now,

Required direction cosines are

Answer (d) 7 units