Question

If `A= <4, 3 ,-1 >` and `B= <8 ,7 ,6 >`, what is `A*B -||A|| ||B||`?

Answer 1

`A·B-[A][B]=-18.6962`

Explanation:

`A=(4,3,-1)` and `B=(8,7,6)` then dot product is

`A·B=32+21-6=47`

By other hand `[A]=sqrt(4^2+3^2+1^2)=sqrt26`
`[B]=sqrt(8^2+7^2+6^2)=sqrt166`

`A·B-[A][B]=47-sqrt26sqrt166=47-65.6962=-18.6962`