Practicing Success
Value of $[\vec{a} \times \vec{b}, \vec{a} \times \vec{c}, \vec{d}]$ is always equal to: |
$(\vec{a}. \vec{d})[\vec{a} \vec{b} \vec{c}]$ $(\vec{a} . \vec{c})[\vec{a} \vec{b} \vec{c}]$ $(\vec{a} . \vec{b})[\vec{a} \vec{b} \vec{c}]$ None of these |
$(\vec{a}. \vec{d})[\vec{a} \vec{b} \vec{c}]$ |
${[\vec{a} \times \vec{b}, \vec{a} \times \vec{c}, \vec{d}]}$ $=(\vec{a} \times \vec{b}) .((\vec{a} \times \vec{c}) \times \vec{d})$ $=(\vec{a} \times \vec{b}) .((\vec{a} . \vec{d}) \vec{c}-(\vec{c} . \vec{d}) \vec{a})$ $=(\vec{a} . \vec{d})[\vec{a} \vec{b} \vec{c}]$ Hence (1) is correct answer. |