Question

Let vector a = 2i + j - 2k and vector b = i + j. If vector c is a vector such that a.c = |c|, |c - a| = 2√2 and the angle between (a x b) and c is 30°, then the value of |(a x b) x c| is

(A) 2/3 

(B) 3/2 

(C) 2 

(D) 3

Answer 1

Answer is (B) Cannot be evaluated

Since vector r.a = 0, r.b = 0 and r.c = 0; vector r must be perpendicular to all the three vectors a,b and c. Hence vectors a, b, and c  must be coplanar. So,

vector [abc] = 0