MCQ
${\tan ^{ - 1}}1 + {\tan ^{ - 1}}2 + {\tan ^{ - 1}}3 = $
  • A
    $\frac{\pi }{2}$
  • B
    $\frac{\pi }{4}$
  • C
    $0$
  • None of these

Answer

Correct option: D.
None of these
d
(d) ${\tan ^{ - 1}}1 + {\tan ^{ - 1}}2 + {\tan ^{ - 1}}3$

$ = {\tan ^{ - 1}}1 + \pi + {\tan ^{ - 1}}\left( {\frac{5}{{ - 5}}} \right)$

$ = {\tan ^{ - 1}}1 + \pi - {\tan ^{ - 1}}1 = \pi $.

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