Question

If `A= <-3 ,4 ,-1 >` and `B= <8 ,-4 ,2 >`, what is `A*B -||A|| ||B||`?

Answer 1

The answer is `=(-42-sqrt2184)`

Explanation:

The dot product is `vecA.vecB`
`=〈-3,4,-1〉.〈8,-4,2〉=-24-16-2=-42`

The modulus of `vecA=∥vecA∥=sqrt(9+16+1)=sqrt26`

The modulus of `vecB=∥vecB∥=sqrt(64+16+4)=sqrt84`

`vecA.vecB-∥vecA∥∥vecB∥=-42-sqrt(26*84)=-42-sqrt2184`