If A= <2 ,6 ,-3 > and B= <-6 ,2 ,7 >, what is A*B -||A|| ||B||?

1 Answer
Narad T.
Nov 1, 2016

The answer is =-21-7sqrt89

Explanation:

The dot product vecA.vecB=〈2,6,-3〉.〈-6,2,7〉
=2*-6+6*2+7*-3=-12+12-21=-21
The modulus of vecA , =∥vecA∥=∥〈2,6,-3〉∥=sqrt(4+36+9)
=sqrt49=7
The modulus of vecB , =∥vecB∥=∥〈-6,2,7〉∥=sqrt(36+4+49)
=sqrt89
And finally we have (vecA.vecB-∥vecA∥*∥vecB∥)=-21-7sqrt89

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