Example 1. Are the vectors $\vec{p}$ and $\vec{q}$ perpendicular, if $\vec{p}=$ $=\{2,0,-3\}, \vec{q}=\{3,4,2\}$?
Solution. The condition of perpendicularity of vectors (point $2^{\circ}$ ) $\vec{p} \vec{q}=0$; in our case

$$
\vec{p} \vec{q}=2 \cdot 3+0 \cdot 4-3 \cdot 2=0 \Rightarrow \vec{p} \perp \vec{q}
$$

Answer. Yes.