Trong không gian $Oxyz,$ góc giữa hai vectơ $\overrightarrow{j}=\left( 0;1;0 \right)$ và $\overrightarrow{u}=\left( 1;-\sqrt{3};0 \right)$ là

$\cos \left( \overrightarrow{j};\overrightarrow{u} \right)=\dfrac{\vec{j}.\vec{u}}{\left| {\vec{j}} \right|.\left| {\vec{u}} \right|}=\dfrac{0.1+1.\left( -\sqrt{3} \right)+0.0}{\sqrt{{{0}^{2}}+{{1}^{2}}+{{0}^{2}}}.\sqrt{{{1}^{2}}+{{\left( -\sqrt{3} \right)}^{2}}+{{0}^{2}}}}=\dfrac{-\sqrt{3}}{2}\Rightarrow \left( \overrightarrow{j};\overrightarrow{u} \right)={{150}^{0}}.$