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The vectors which is/are coplanar with vectors `hati+hatj+2hatk and hati+2hatj+hatk` and perpendicular to the vector `hati+hatj+hatk ` is /are (A) `hatj-hatk` (B) `-hati+hatj` (C) `hati-hatj` (D) `-hatj+hatk`A. `hatj - hatk`B. `-hati + hatj`C. `hati -hatj`D. `-hatj +hatk` |
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Answer» Correct Answer - a,d Any vector in the plane of `veca = hati +hatj + 2hatk and vecb = hati + 2hatj + hatk` is `vecr=lamda(hati+hatj+2hatk) +mu(hati+2hatj+hatk)` `= (lamda+mu)hati+(lamda+2mu)hatj= (2lamda+mu)hatk` Also `vecr` is perpendicular to the vector `hati + hatj +hatk` `Rightarrow vecr.vecc=0` ` Rightarrow lamda + mu =0` Possible vectors are `hatj -hatk or -hatj +hatk` |
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