12. Let S= (1 m) + (2 m) + (2 m)k and T = (3 m)i + (4 m)k. The angle between these two vectors is given by: A) cos-1(14/15) B) cost1(11/225) C) cos-(104/225) D) cost1(11/15) E) cannot be found since ~ and ' do not lie in the same plane 13. Which of the following is correct? A) Multiplying a vector by a scalar gives a scalar result. B) Multiplying a vector by a vector always gives a vector result. C) Multiplying a vector by a vector never gives a scalar result. D) The only type of vector multiplication that gives a scalar result is the dot product. E The only type of vector multiplication that gives a vector result is the cross product. 14. The result of ( x k) x (kxD) is: A) 0 B) +1 C ) D) E) K 15. The value of k . (k x D) is: A) B ) +1 C ) -1 D ) 3 1/3 E)