Let →a=a1^i+a2^j+a3^k,→b=b1^i+b2^j+b3^k,→c=c1^i+c2^j+c3^k.If ∣∣→c∣∣=1 and (→a×→b)×→c=0then ∣∣
∣∣a1a2a3b1b2b3c1c2c3∣∣
∣∣2=
A
0
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B
1
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C
∣∣→a∣∣2∣∣∣→b∣∣∣2
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D
∣∣∣→a×→b∣∣∣2
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Solution
The correct option is D∣∣∣→a×→b∣∣∣2 (→a×→b)×→c=0 ⇒→c is parallel to →a×→b Given ∣∣→c∣∣=1⇒→c=→a×→b∣∣∣→a×→b∣∣∣ ∴→a×→b.→c=∣∣∣→a×→b∣∣∣2∣∣∣→a×→b∣∣∣ Hence ∣∣
∣∣a1a2a3b1b2b3c1c2c3∣∣
∣∣2=∣∣∣→a×→b∣∣∣2