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Let `veca=(1,1,-1), vecb=(5,-3,-3)` and `vecc=(3,-1,2)`. If `vecr` is collinear with `vecc` and has length `(|veca+vecb|)/(2)`, then `vecr` equalsA. `+-3vecc`B. `+-3/2vecc`C. `+-vecc`D. `+-2/3vecc` |
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Answer» Correct Answer - C We have, `vecr=lambdavecc` Given, `|vecr|=|lambda||vecr|` `therefore |6hati-2hatj-hatk|=2|lambda||3hati-hatj+2hatk|` `therefore sqrt(56) = 2|lambda|sqrt(14)` `therefore lambda=+-1` `therefore vecr=+-vecc` |
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