aˉ=i^+2j^−3k^aˉ=2i^+j^−k^aˉ×rˉ=aˉ×bˉ;aˉ⋅rˉ=0⇒aˉ×(rˉ−bˉ)=0⇒aˉ=λ(rˉ−bˉ)aˉ⋅aˉ=λ(aˉ⋅rˉ−aˉ⋅bˉ)14=−7λ⇒λ=−22−aˉ=rˉ−bˉ⇒rˉ=bˉ−2aˉ=22bˉ−aˉ=23i^+k^
Statement (I) is incorrect $\begin{aligned}
& \cos 2 \mathrm{A}+\cos 2 \mathrm{B}+\cos 2 \mathrm{c} \geq-\frac{3}{2} \
& 2 \mathrm{A}+2 \mathrm{B}+2 \mathrm{C}=2 \pi \
& \cos 2 \mathrm{A}+\cos 2 \mathrm{B}+\cos 2 \mathrm{C} \
& =-1-4 \cos \mathrm{A} \cdot \cos \mathrm{B} \cdot \cos \mathrm{C} \
& \geq-1-4 \times \frac{1}{2} \times \frac{1}{2} \times \frac{1}{2} \
& =-\frac{3}{2}
\end{aligned}$
Statement (II) is correct.