Question

If volume of parallelopiped whose there coterminous edges are vector u = i + j + λk, vector v = 2i + j + k & vector w = i + j + 3k is 1 cubic unit then cosine of angle between u and v is

(1) 7/3√10

(2) 7/6√3

(3) 5/3√3

(4) 5/7

Answer 1

Answer is (2) 7/6√3