Question

The value of $\cos 2 \theta$ in terms of $\cot \theta$ is

• A. $\frac{\cot ^2 \theta+1}{\cot ^2 \theta-1}$
• B. $-\frac{1+\cot ^2 \theta}{\cot ^2 \theta-1}$
• C. $\frac{\cot ^2 \theta-1}{\cot ^2 \theta+1}$
• D. $\frac{1-\cot ^2 \theta}{1+\cot ^2 \theta}$

Answer 1

Answer: (C)

Use $\cos 2 \theta=\frac{1-\tan ^2 \theta}{1+\tan ^2 \theta}$