Question

If r, a, b, c are non null vectors such that , then

• A. Is equal to 1
• B. Cannot be evaluated
• C. Is equal to zero
• D. None of these

Answer 1

Answer: (C)

Is equal to zero

Answer 2

Since = 0, and , must be perpendicular to all the three vectors $\overline { \mathrm { a } } , \overline { \mathrm { b } }$ and $\overline { \mathrm { c } }$. Hence $\overline { \mathrm { a } } , \overline { \mathrm { b } }$ and $\overline { \mathrm { c } }$must be coplanar

̃ $[ \bar { a } \bar { b } \bar { c } ]$ =0