If the angle between \(\hat{i}+\hat{k}\) and \(\hat{i}+\hat{j}+a \hat{k}\) is \(\frac{\pi}{3}\), then the value of a is
A. 0 or 2
B. -4 or 0
C. 0 or -3
D. 2 or -2
Answer:B
If the angle between \(\hat{i}+\hat{k}\) and \(\hat{i}+\hat{j}+a \hat{k}\) is \(\frac{\pi}{3}\), then the value of a is
A. 0 or 2 B. -4 or 0 C. 0 or -3 D. 2 or -2