Question
For the principal value, evaluate $\cot \left[\sin ^{-1}\left\{\cos \left(\tan ^{-1} 1\right)\right\}\right]$

Answer

We know that  $\tan ^{-1} 1=\frac{\pi}{4}$
$\therefore \cot \left[\sin ^{-1}\left\{\cos \left(\tan ^{-1} 1\right)\right\}\right]$
$=\cot \left\{\sin ^{-1}\left(\cos \frac{\pi}{4}\right)\right\}$
$=\cot \left(\sin ^{-1} \frac{1}{\sqrt{2}}\right)$
$=\cot \frac{\pi}{4}$
$=1$

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