Question

Find `|veca xx vecb|`, if `veca = hati - 7hatj + 7hatk` and  `vecb = 3hati - 2hatj + 2hatk`

Options

• `19sqrt(2)`

• `sqrt(2)`

• `17sqrt(2)`

• `18sqrt(2)`

Answer 1

`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)`