2. If $\overrightarrow{v}=(a,b,c)$, then $\overrightarrow{v}=a\cdot\overrightarrow{i}+b\cdot \overrightarrow{j}+c\cdot\overrightarrow{k}$
and $|\overrightarrow{v}|=\sqrt{a^2+b^2+c^2}$