What is the angle between two vectors.A=i-j and B=i+k?

1 Answer
Jun 28, 2018

#= pi/3#

Explanation:

  • #{(bbA=bbi-bbj ), (bb B=bbi+bbk):}#

#bbA * bbB = abs bbA abs bbB cos alpha#

From that definition:

  • #cos alpha = (bbA * bbB)/(abs bbA abs bbB) #

  • #bbA * bbB = (:1, -1, 0:)*(:1, 0, 1:) = 1#

  • #abs bbA = sqrt2#

  • #abs bbB = sqrt2#

#implies cos alpha = 1/2#

# implies alpha = arccos (1/2)= pi/3#