hati-hatj ও  hatj-hatk এদের মধ্যবর্তী কোণ-

Explanation:

Another Explanation (5): ধরি, \(\vec{a} = \hat{i} - \hat{j}\) এবং \(\vec{b} = \hat{j} - \hat{k}\) \(\vec{a}\) ও \(\vec{b}\) এর মধ্যবর্তী কোণ \(\theta\) হলে, \(\cos \theta = \frac{\vec{a} \cdot \vec{b}}{|\vec{a}| |\vec{b}|}\) এখন, \(\vec{a} \cdot \vec{b} = (\hat{i} - \hat{j}) \cdot (\hat{j} - \hat{k}) = (0 - 1 + 0) = -1\) 😥 \(|\vec{a}| = \sqrt{1^2 + (-1)^2} = \sqrt{2}\) \(|\vec{b}| = \sqrt{1^2 + (-1)^2} = \sqrt{2}\) সুতরাং, \(\cos \theta = \frac{-1}{\sqrt{2} \cdot \sqrt{2}} = \frac{-1}{2}\) 😔 \(\theta = \cos^{-1} \left( -\frac{1}{2} \right)\) আমরা জানি, \(\cos 120^\circ = -\frac{1}{2}\) অতএব, \(\theta = 120^\circ\) 😄