Unit vector →r which satisfies →r×→b=→r×→c where →b=ˆi+2ˆj+ˆk & →c=3ˆi+2ˆk, is
A
±(2ˆi−2ˆj+ˆk3)
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B
±(2ˆi+2ˆj+ˆk3)
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C
±(ˆi+ˆj+ˆk√3)
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D
±ˆi
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Solution
The correct option is B±(2ˆi−2ˆj+ˆk3) Given →b=ˆi+2ˆj+ˆk & →c=3ˆi+2ˆk →r×→b=→r×→c (→r×→b)−(→r×→c)=→0 ⇒→r×(→b−→c)=→0 ⇒→r=λ(→b−→c)=λ(−2ˆi+2ˆj−ˆk) ⇒ˆr=±(2ˆi−2ˆj+ˆk3)