Explanation: 
Another Explanation (5):
cos75° এর মান নির্ণয়:
আমরা জানি, cos(A + B) = cosA cosB - sinA sinB
cos75° = cos(45° + 30°)
= cos45° cos30° - sin45° sin30°
আমরা জানি, cos45° = \( \frac{1}{\sqrt{2}} \) , cos30° = \( \frac{\sqrt{3}}{2} \) , sin45° = \( \frac{1}{\sqrt{2}} \) , sin30° = \( \frac{1}{2} \)
সুতরাং,
cos75° = \( \frac{1}{\sqrt{2}} \cdot \frac{\sqrt{3}}{2} - \frac{1}{\sqrt{2}} \cdot \frac{1}{2} \)
= \( \frac{\sqrt{3}}{2\sqrt{2}} - \frac{1}{2\sqrt{2}} \)
= \( \frac{\sqrt{3} - 1}{2\sqrt{2}} \)
অতএব, cos75° = \( \frac{\sqrt{3} - 1}{2\sqrt{2}} \) 🥳🥳🥳
