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प्रश्न
Find `|veca xx vecb|`, if `veca = hati - 7hatj + 7hatk` and `vecb = 3hati - 2hatj + 2hatk`
विकल्प
`19sqrt(2)`
`sqrt(2)`
`17sqrt(2)`
`18sqrt(2)`
MCQ
उत्तर
`19sqrt(2)`
Explanation:
We have `veca = hati - 7hatj + 7hatk, b = 3hati - 2hatj + 2hatk`
`veca xx vecb = |(hati, hatj, hatk),(1, -7, 7),(3, -2, 2)|`
= `(- 14 + 14)hati - (2 - 21)hatj + (-2 + 21)hatk`
= `-(19)hatj + 19hatk`
= `19hatj + 19hatk`
`|veca xx vecb| = sqrt((19)^2 + (19)^2`
= `19sqrt(1 + 1)`
= `19sqrt(2)`
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