Question

Let $\theta$ be the angle between the planes $P_1: \vec{r} \cdot(\hat{i}+\hat{j}+2 \hat{k})=9$ and $P_2: \hat{r} \cdot(2 \hat{i}-\hat{j}+\hat{k})=15$ Let $L$ be the line that meets $P_2$ at the point $(4,-2,5)$ and makes an angle $\theta$ with the normal of $P_4$ If $\alpha$ is the angle between $L$ and $P_2$, then $\left(\tan ^2 \theta\right)\left(\cot ^2 \alpha\right)$ is equal to

Answer 1

The correct answer is 9.

cosθ=6(i^+j^​+2k^)⋅(2i^−j^​+k^)​=62−1+2​=21​
θ=π/3
α=π/6
(tan2θ)(cot2α)
(3)(3)=9