If A→=i^+2k^−k^,B→=−i^+j^−2k^  then angle between A→  and B→  is

A→=i^+2j^−k^;B→=i^+j^−2k^ A=|A→|=12+22(−1)2=6 B=|B→|=(−1)2+12(−2)2=6 A→.B→=(i^+2j^−k^).(−i^+j^−2k^)         =−1+2+2=3 If θ is angle between A→  and B→ , then A→.B→=ABcosθ                3=66cosθ cosθ=36=12  or θ=π3