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Let `veca` and `vecb` be two non-collinear unit vectors. If `vecu=veca-(veca.vecb)vecb` and `vec=vecaxxvecb`, then `|vecv|` isA. `|vecu|`B. `|vecu|+ |vecu.vecb|`C. `|vecu| + |vecu .veca|`D. none of these |
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Answer» Correct Answer - b,d `vecu = vecas - ( veca . Vecb) vecb` ` vecb xx (veca xx vecb)` ` Rightarrow |vecu| = |vecb xx (veca xx vecb)|` ` |vecb| |veca xx vecb| sin 90 ^(@)` ` |vecb||veca xx vecb|` ` |vecv|` Also ` vecu . Vecb = vecb.vecb xx (veca xx vecb)` ` [vecb vecb veca xx vecb]` =0 ` Rightarrow |vecv| = |vecu| + |vecu. vecb|` |
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