A) a
B) b
C) c
D) 0
Correct Answer: B
Solution :
\[a\times (b\times c)=(a\,.\,c)\,b-(a\,.\,b)\,c\] \[\because \,\,\,\,\mathbf{a}\,\bot \,\,\mathbf{b}\,\,,\,\,\,\therefore \,\,\,\mathbf{a}\,.\,\mathbf{b}=0\] \[\because \,\] \[\mathbf{a}|\,|\mathbf{c}\], \[\therefore \,\,\,\mathbf{a}\,.\,\mathbf{c}=1\] (a, b and c are unit vectors) \[\mathbf{a}\times (\mathbf{b}\times \mathbf{c})=(1)\mathbf{b}-(0)\,\mathbf{c}\,\]= b.
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