Question

Let A= [1, 2] and B= [2,4] .The what is d (A, B)?​

Answer 1

Answer:

Correct option is

D

3

1

,

3

−1

,

3

−1

Let the direction cosines of the line be (a,b,c)

Since it's equally inclined to OA,OB,OC

3

a+2b+2c

=

7

2a+3b+6c

=

13

3a+4b+12c

=k

⇒a+2b+2c=3k...(1)

2a+3b+6c=7k....(2)

3a+4b+12c=13k....(3)

Eliminating a from (1) and (2), we get

b−2c=−k....(3)

Similarly, eliminating a from (1) and (3), we get

2b−6c=−4k...(4)

From (3) and (4), we get b=c=k...(5)

Using the above value in (1) we get a=−k....(6)

From (5) and (6), a:b:c=−1:1:1

Also, a

2

+b

2

+c

2

=1⇒k=±

3

1

Hence, direction cosines are (−

3

1

,

3

1

,

3

1

) or (

3

1

,−

3

1

,−

3