If a and b are two unit vectors such that a +2 b and 5 a -4 b are perpendicular to each other, then the angle between a and b is

Step-by-step solution

Since a +2 b and 5 a -4 b are perpendicular to each other aligned & ( a +2 b ) (5 a -4 b )=0 & 5| a |^2-8| b |^2+6 a b =0 & -3+6| a || b | =0 [ | a |=| b |=1] & = 1 2 & = 3 aligned