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If the direction cosines of two lines ar...


If the direction cosines of two lines are `(l_(1), m_(1), n_(1))` and
`(l_(2), m_(2), n_(2))` and the angle between them is `theta` then
`l_(1)^(2)+m_(1)^(2)+n_(1)^(2)=1=l_(2)^(2)+m_(2)^(2)+n_(2)^(2)`
and costheta `= l_(1)l_(2)+m_(1)m_(2)+n_(1)n_(2)`
The angle between the lines whose direction
cosines are `(1/2, 1/2,1/sqrt(2)) and (-1/2, -1/2, 1/sqrt(2))` is

A

`0^(@)`

B

`60^(@)`

C

`90^(@)`

D

`120^(@)`

Text Solution

Verified by Experts

The correct Answer is:
C
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