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Vectors perpendicular to`hati-hatj-hatk` and in the plane of `hati+hatj+hatk and -hati+hatj+hatk` are (A) `hati+hatk` (B) `2hati+hatj+hatk` (C) `3hati+2hatj+hatk` (D) `-4hati-2hatj-2hatk`A. `hati + hatk`B. `2hati + hatj + hatk`C. `3hati+ 2 hatj + hatk`D. `-4 hati - 2hatj - 2hatk` |
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Answer» Correct Answer - b,d Let `alpha =hati - hatj -hatk , vecbeta = hati + hatj +hatk` ` and vecgmma = -hati +hatj +hatk` Let requried vector, `veca=xhati + yhatj +zhatj` then `vecalpha, vecbeta, vecgamma` are coplanar, i.e. `|{:(x,y,z),(1,1,1),(-1,1,1):}|=0or y=z` Also `veca and vecalpha` are perpendicular, ` Rightarrow x-y -z =0` `Rightarrow x = zy` |
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