tanθ=1/7 হলে  cos2θ এর মান কত? 

Explanation:

Another Explanation (5): দেওয়া আছে, \( \tan \theta = \frac{1}{7} \). আমরা জানি, \[ \cos 2\theta = \frac{1 - \tan^2 \theta}{1 + \tan^2 \theta} \] এখানে, \( \tan \theta = \frac{1}{7} \) বসালে পাই, \[ \cos 2\theta = \frac{1 - (\frac{1}{7})^2}{1 + (\frac{1}{7})^2} \] \[ = \frac{1 - \frac{1}{49}}{1 + \frac{1}{49}} \] \[ = \frac{\frac{49 - 1}{49}}{\frac{49 + 1}{49}} \] \[ = \frac{\frac{48}{49}}{\frac{50}{49}} \] \[ = \frac{48}{49} \times \frac{49}{50} \] \[ = \frac{48}{50} \] \[ = \frac{24}{25} \] সুতরাং, \( \cos 2\theta = \frac{24}{25} \). 🎉🎉