Let $\vec{a}, \vec{b}, \vec{c}$ be three unit vectors such that $\vec{a}+5 \vec{b}+3 \vec{c}=\vec{0}$ Then $\vec{a} .(\vec{b} \times \vec{c})$ is equal to:
Answer & explanation
Correct answer: option 4
$\vec{a}+5 \vec{b}+3 \vec{c}=\vec{0}$
Thus $\vec{a}, \vec{b}, \vec{c}$ are coplaner.
Hence $\vec{a} .(\vec{b} \times \vec{c})=0$
Hence (4) is correct answer.