Question

Find the angle between vectors A and B. Here A= ^i +2^j -^k and B= -^i+^j-2^k.

Answer 1

dot product:  -1 +2 + 2 = 3

magnitudes =  √(1+4+1)
and    √(1+4+1) 

cosine of angle =  3/(2√6)  
angle = 52.2 deg