If the vectors $\vec a,\vec b,\vec c$ and $\vec d$ are coplanar vectors, then $(\vec a×\vec b)×(\vec c×\vec d)$ is equal to
Answer & explanation
Correct answer: option 2
Clearly, $\vec a×\vec b$ is parallel to $\vec c×\vec d$.
$∴(\vec a×\vec b)×(\vec c×\vec d)=\vec 0$