$\vec{A} = \hat{i} - \hat{j} + \hat{k} ও \vec{B} = - \hat{i} + \hat{j} + 2 \hat{k}$

ভেক্টর দুইটির অন্তর্ভুক্ত কোণ নির্ণয় কর? 

$\begin{array}{l} \overrightarrow{\mathrm{A}}=\hat{\mathrm{i}}-\hat{\mathrm{j}}+\hat{\mathrm{k}} ; \overrightarrow{\mathrm{B}}=\hat{\mathrm{i}}+\hat{\mathrm{j}}+2 \hat{\mathrm{k}} \Rightarrow \theta=\cos ^{-1}\left(\frac{\overrightarrow{\mathrm{A}} \cdot \overrightarrow{\mathrm{B}}}{|\overrightarrow{\mathrm{A}}||\overrightarrow{\mathrm{B}}|}\right) \\ =\theta=\cos ^{-1} \frac{-1-1+2}{\sqrt{1^{2}+1^{2}+1^{2}} \sqrt{1^{2}+1^{2}+2^{2}}}=\cos ^{-1}(0)=90^{\circ}\end{array}$