1.

Let `veca=hatj-hatk` and `vecc=hati-hatj-hatk`. Then the vector `vecb` satisfying `vecaxxvecb+vecc=vec0` and `veca.vecb=3` isA. `-hati+hatj-2hatk`B. `2hati-hatj+2hatk`C. `hati-hatj-2hatk`D. `hati+hatj-2hati`

Answer» Correct Answer - A
Given , `a xx b + c = 0`
`rArr a xx (a xx b) + a xx c = 0`
`rArr (a.b)a - (a.a) + a xx c = 0`
`rArr 3a - 2b +a xx c = 0`
`rArr 2b = 3a+ a xx c`
`rArr 2b = 3hatj - 3hatk -2hati - hatj - hatk`
`rArr 2b = - hati + 2hatj - 4hatk`
`:. b = - hati + hatj - 2hatk`


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