1.

If the angle betweenthe lines whose direction cosines are (-(2)/(sqrt(21)), (C )/(sqrt(21)), (1)/(sqrt(21))) and ((3)/(sqrt(54)), (3)/(sqrt(54)), -(6)/(sqrt(54))) is (pi)/(2), then the value of C is

Answer»

4, 1
1, 4
`-1,-4`
`-6,-3`

ANSWER :A


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