# What is the dot product of <-8,1,2 >  and <-2,5,-1 > ?

May 18, 2018

The answer is $= 19$

#### Explanation:

The dot product of $2$ vectors

$\vec{x} = < a , b , c >$

and

$\vec{y} = < d , e , f >$

is

$\vec{x} . \vec{y} = < a , b , c > . < d , e , f > = a d + b e + c f$

Therefore,

$< - 8 , 1 , 2 > . < - 2 , 5 , - 1 > = \left(- 8\right) \cdot \left(- 2\right) + \left(1\right) \cdot \left(5\right) + \left(2\right) \cdot \left(- 1\right)$

$= 16 + 5 - 2$

$= 19$