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Let `veca, vecb and vecc` be non-zero vectors such that no two are collinear and `(vecaxxvecb)xxvecc=1/3 |vecb||vecc|veca` if `theta` is the acute angle between vectors `vecb and vecc` then find value of `sin theta`. |
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Answer» we have `(veca xx vecb ) xx vecc = 1/3 |vecb||vecc|veca` `or (veca .vecc) vecb - (vecb .vecc)veca = 1/3 |vecb||vecc|veca` `or (veca. Vecc) vecb- {(vecb.vecc) + 1/3 |vecb|vecc|} veca =vec0` `Rightarrow veca.vecc =0 and vecb.vecc + 1/3 |vecb|vecc|=0` (`veca and vecb` are non-collinear) or `|vecb||vecc|cos theta+ 1/3 |vecb |vecc| =0` `or cos theta = -1//3` `Rightarrow sin theta = sqrt(8/9) = ( 2sqrt2)/3` |
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