Question

The value of $\cot \left({\tan }^{-1}a+{\cot }^{-1}a\right)$ is

• A. 0
• B. 1
• C. $-1$
• D. $\infty$

Answer 1

Answer: (A)

We have,
$\cot \left({\tan }^{-1}a+{\cot }^{-1}a\right)=\cot \frac{\pi }{2}=0\left[\because {\tan }^{-1}x+{\cot }^{-1}x=\frac{\pi }{2}\right]$