# Find the values of each of the following:    12. $\cot(\tan^{-1}a + \cot^{-1}a)$

We have to find the value of   $\cot(\tan^{-1}a + \cot^{-1}a)$
As we know $\left [\because \tan^{-1}x + \cot^{-1} x = \frac{\pi}{2} \right ]$   so,
Equation reduces to $\cot(\frac{\pi}{2}) = 0$.