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If the unit vectors ` veca and vecb ` are inclined of an angle ` 2 theta` such that ` |veca -vecb| lt 1 and 0 le theta le pi` then ` theta` in the intervalA. `[0, pi//6)`B. `(5 pi//6, pi]`C. `[pi//6, pi//2]`D. `(pi//2, 5pi//6]` |
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Answer» Correct Answer - a,b we have `|veca -vecb|^(2) = |veca|^(2) + |vecb|^(2) -2 (veca. Vecb)` `or |vec-vecb|^(2) = |veca |^(2) + |vecb|^(2) -2 |veca||vecb|cos2theta` ` |veca -vecb|^(2) = 2 - 2cos theta " " (|veca|=|vecb|=1)` ` = 4sin^(2) theta ` ` or |veca -vecb| =2 |sin theta|` Now, `|veca- vecb| gt 1` ` Rightarrow 2|sin theta|lt 1` ` or |sin theta| lt 1/2 ` ` Rightarrrow theta in [ 0, pi//6) or theta in ( 5 pi//6, pi]` |
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