`u = ` Use the dot product to find the magnitude of u.

The magnitude of a vector `u` is the square root of its product by itself, because

`u*u=||u||*||u||*cos(theta),`

`and theta=0,` `cos(theta)=1.` So

`||u||=sqrt(u*u)=sqrt(lt4,-6gt*lt4,-6gt)=`

`=sqrt(4*4+(-6)*(-6))=sqrt(16+36)=sqrt(52)=2sqrt(13) approx 7.2.`

The magnitude of a vector `u` is the square root of its product by itself, because

`u*u=||u||*||u||*cos(theta),`

`and theta=0,` `cos(theta)=1.` So

`||u||=sqrt(u*u)=sqrt(lt4,-6gt*lt4,-6gt)=`

`=sqrt(4*4+(-6)*(-6))=sqrt(16+36)=sqrt(52)=2sqrt(13) approx 7.2.`