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Q. If $3\, \tan^{-1}x+\cot^{-1}x=\pi$ then $x$ is equal to

KCETKCET 2016Inverse Trigonometric Functions

Solution:

Solution: We have $3 \tan ^{-1} x+\cot ^{-1} x=\pi$
$\Rightarrow 2 \tan ^{-1} x+\tan ^{-1} x+\cot ^{-1} x=\pi$
$\Rightarrow 2 \tan ^{-1} x+\frac{\pi}{2}=\pi $
${\left[\because \tan ^{-1} x+\cot ^{-1} x=\frac{\pi}{2}\right]} $
$\Rightarrow 2 \tan ^{-1} x=\pi-\frac{\pi}{2}$
$\Rightarrow 2 \tan ^{-1} x=\frac{\pi}{2}$
$\Rightarrow \tan ^{-1} x=\frac{\pi}{4} $
$\Rightarrow x=\tan \frac{\pi}{4} $
$\therefore x=1$