Answer
$\frac{\vec u\cdot\vec v}{|\vec u||\vec v|}$, $0$, $0$, $ perpendicular$.
Work Step by Step
If we know two vectors $\vec u$ and $\vec v$, we can calculate the angle $\theta$ between them using the formula $cos\theta=\frac{\vec u\cdot\vec v}{|\vec u||\vec v|}$. If the two vectors are perpendicular to each other, we have $\theta=90^{\circ}$ and $cos\theta=0$, so that $\vec u\cdot\vec v=0$. In the case that
$\vec u=\langle 4,5,6\rangle$ and $\vec v=\langle 3,0,-2\rangle$, we have
$\vec u\cdot\vec v= 4\times3+5\times0+6\times(-2)=0$, thus we know that these two vectors are $ perpendicular$ to each other.
