Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Vectors

Question:

If $\vec a,\vec b,\vec c$ are any three vectors such that $(\vec a+\vec b).\vec c=(\vec a-\vec b).\vec c = 0$, then $(\vec a×\vec b)×\vec c$ is

Options:

$\vec 0$

$\vec a$

$\vec b$

none of these

Correct Answer:

$\vec 0$

Explanation:

We have,

$(\vec a+\vec b).\vec c=(\vec a-\vec b).\vec c = 0⇒\vec b.\vec c=0=\vec a.\vec c$

$∴(\vec a×\vec b)×\vec c=(\vec c.\vec a)\vec b-(\vec c.\vec b)\vec a=\vec 0$