The angle between the planes \(r \cdot(\hat{i}+2 \hat{j}+\hat{k})=4\) and \(r(-\hat{i}+\hat{j}+2 \hat{k})=9\) is
A. 30°
B. 60°
C. 45°
D. None of these
Answer:B
The angle between the planes \(r \cdot(\hat{i}+2 \hat{j}+\hat{k})=4\) and \(r(-\hat{i}+\hat{j}+2 \hat{k})=9\) is
A. 30° B. 60° C. 45° D. None of these