If →u,→v,→w are three non-zero and non-coplanar vectors, then (→u+→v−→w)⋅[(→u−→v)×(→v−→w)] is equal to:
A
0
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B
→u⋅(→v×→w)
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C
→u⋅(→w×→v)
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D
3→u⋅(→v×→w)
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Solution
The correct option is B→u⋅(→v×→w) Let (→u+→v−→w)⋅[(→u−→v)×(→v−→w)]=E ⇒E=(→u+→v−→w)⋅[(→u×→v)−(→u×→w)−0+(→v×→w)]
Now, on multiplying (taking dot product) each term, we have: ⇒E=→u⋅→v×→w−→v⋅→u×→w−→w⋅→u×→v ⇒E=[→u→v→w]+[→u→v→w]−[→u→v→w] ⇒E=→u⋅(→v×→w)