In a triangle \(A B C\), the sides \(A B\) and \(A C\) are represented by the vectors \(3 \hat{i}+\hat{j}+\hat{k}\) and \(\hat{i}+2 \hat{j}+\hat{k}\) respectively. Calculate the angle \(\angle A B C\)
(A) \(\cos ^{-1} \sqrt{\frac{5}{11}}\)
(B) \(\cos ^{-1} \sqrt{\frac{6}{11}}\)
(C) \(\left(90^{\circ}-\cos ^{-1} \sqrt{\frac{5}{11}}\right)\)
(D) \(\left(180^{\circ}-\cos ^{-1} \sqrt{\frac{5}{11}}\right)\)
Ans: (A)
