Let →a=^i−^j,→b=→j−^k,→c=^k−^i.If→d is a unit vector such that →a.→d=0=[→b→c→d], then →d equals
A
±^i+^j−2^k√6
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B
±^i+^j−^k√3
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C
±^i+^j+^k√3
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D
±^k
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Solution
The correct option is A±^i+^j−2^k√6 Let →d=x^i+y^j+z^k
where, x2+y2+z2=1...(i) [∵d being unit vector]
Since, →a.→d=0⇒x−y=0⇒x=y...(ii)Also,[→b→c→d]=0⇒∣∣
∣∣01−1−101xyz∣∣
∣∣=0⇒x+y+z=0⇒2x+z=0[fromEq.(ii)]...(iii)FromEq.(i),(ii)and(iii)x2+x2+4x2=1⇒x=±1√6∴→d=±1√6(^i+^j−2^k)