Question

If `veca = << 7,-2,1 >>` and `vecb = << -2,6,7 >>`, what is `vecacdotvecb - ||veca||cdot||vecb||`?

Answer 1

`-19-sqrt(54*89)`

Explanation:

`veca=(7,-2,1)`
`vecb=(-2,6,7)`
Dot product is
`veca.vecb=7*-2-2*6+7*1=-14-12+7=-19`
`∣∣veca∣∣=sqrt(7^2+2^2+1)=sqrt54`
`∣∣vecb∣∣=sqrt(2^2+6^2+7^2)=sqrt89`
So the answer is
`veca.vecb-∣∣veca∣∣.∣∣vecb∣∣=-19-sqrt(54*89)`