If vector a, b, c and d are unit vectors such that (a x b).(c x d) = 1 and a.c = 1/2, then
(A) a, b, c are non-coplanar
(B) b, c, d are non-coplanar
(C) b, d, are non-parallel
(D) a, d, are parallel and b c , are parallel
Answer is**(C) b, d, are non-parallel**
The given equation, (a x b) . (c x d) = 1, is possible only when
|a x b| = |c x d| = 1
Therefore, we conclude that the vectors b and d are non-parallel.
