If $A= <2 ,8 ,-4 >$ and $B= <3 ,2 ,7 >$ , what is $A*B -||A|| ||B||$ ?

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Answer 1 · 2017-05-31T08:36:38

The result is $=-78.17$

The dot product is

$vecA.vecB=<2,8,-4>:<3,2,7>=2*3+8*2-4*7$

$=6+16-28=-6$

The modulus of $vecA$ is

$=||vecA||=||<2,8,-4>||$

$=sqrt(4+64+16)$

$=sqrt(84)$

The modulus of $vecB$ is

$=||vecB||=||<3,2,7>||$

$=sqrt(9+4+49)$

$=sqrt(62)$

So,

$vecA.vecB-||vecA||*||vecB||$

$=-6-sqrt84*sqrt62$

$=-6-72.17$

$=-78.17$

If A= <2 ,8 ,-4 >A= <2 ,8 ,-4 > and B= <3 ,2 ,7 >B= <3 ,2 ,7 >, what is A*B -||A|| ||B||A*B -||A|| ||B||?