If →a,→b,→c be the three non-zero and non-collinar vectors such that →a×→b=→c and →b×→c=→a, then which of the following is/are true
A
→a is perpendicular to →b
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B
→b is perpendicular to →c
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C
|→b|=1
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D
|→b|=2
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Solution
The correct option is C|→b|=1 Given →a=→b×→c ⇒→a=→b×(→a×→b) (∵→a×→b=→c) ⇒→a=(→b⋅→b)→a−(→b⋅→a)→b⇒→a=|→b|2→a−(→b⋅→a)→bComparing both the sides, we get|→b|2=1(→b⋅→a)=0|→b|=1 and →a⋅→b=0∴→a is perpendicular to →b
Now, →c=→a×→b=(→b×→c)×→b=(→b⋅→b)→c−(→c⋅→b)→b→c=|→b|2→c−(→c⋅→b)→bOn comparing both the sides|→b|2=1and (→c⋅→b)=0∴→b is perpendicular to →c