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Question
Find `|veca × vecb|`, if `veca = hati - 7hatj + 7hatk` and `vecb = 3hati - 2hatj + 2hatk`.
Solution
`veca = hati - 7hatj + 7hatk, vecb = 3hati - 2hatj + 2hatk`
`veca xx vecb = |(hati, hatj, hatk), (1, -7, 7), (3, -2, 2)|`
= `hati(-14 + 14) - hatj(2 - 21) + hatk(-2 + 21)`
= `19hatj + 19hatk`
∴ `|veca xx vecb| = sqrt((19)^2 + (19)^2)`
`= 19sqrt(1 + 1)`
`= 19sqrt2`.
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