MCQ
If ${\cot ^{ - 1}}x + {\tan ^{ - 1}}3 = \frac{\pi }{2}$, then $x =$
- A$1/3$
- B$1/4$
- ✓$3$
- D$4$
$ \Rightarrow \,\,{\cot ^{ - 1}}x + {\tan ^{ - 1}}3 = \frac{\pi }{2}\,\, $
$\Rightarrow \,\,{\tan ^{ - 1}}\frac{1}{x} + {\tan ^{ - 1}}3 = \frac{\pi }{2}$
$ \Rightarrow \,\,{\tan ^{ - 1}}\left( {\frac{{\frac{1}{x} + 3}}{{1 - \frac{1}{x}.3}}} \right) = {\tan ^{ - 1}}\left( {\frac{1}{0}} \right)$
$ \Rightarrow \,\,\frac{{3x + 1}}{{x - 3}} = \frac{1}{0}\,\, \Rightarrow \,\,x = 3$
Aliter : As we know that, ${\tan ^{ - 1}}x + {\cot ^{ - 1}}x = \frac{\pi }{2},$
therefore for the given question, $ x$ should be $3.$
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