If →a,→b,→c are non-zero vectors such that →a×(→b×→c) is perpendicular to (→a×→b)×→c, then which of the following is/are true ?
A
→a⋅→b=0
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B
(→a⋅→c)|→b|2=(→a⋅→b)(→b⋅→c)
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C
(→a⋅→c)=0
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D
→b⋅→c=0
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Solution
The correct option is C(→a⋅→c)=0 We have been given ((→a×(→b×→c))⋅((→a×→b)×→c)=0⇒((→a⋅→c)→b−(→a⋅→b)→c)⋅((→a⋅→c)→b−(→b⋅→c)→a)=0 ⇒(→a⋅→c)2|→b|2−(→a⋅→c)(→c⋅→b)(→a⋅→b)−(→b⋅→a)(→a⋅→c)(→b⋅→c)+(→a⋅→b)(→b⋅→c)(→c⋅→a)=0 ⇒(→a⋅→c)2|→b|2=(→a⋅→c)(→a⋅→b)(→c⋅→b) ⇒(→a⋅→c)=0 or (→a⋅→c)|→b|2=(→a⋅→b)(→b⋅→c)