Principal value of \(\tan^{-1}\left(-\sqrt{3}\right) + \tan^{-1}(1)\) is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(-\displaystyle\frac{\pi}{12}\)
The principal value branch of \(\tan^{-1}\) is \(\left(-\frac{\pi}{2}, \frac{\pi}{2}\right)\).
Since \(\tan\left(-\frac{\pi}{3}\right) = -\sqrt{3}\) and \(-\frac{\pi}{3}\) lies in this interval,
\( \displaystyle \tan^{-1}\left(-\sqrt{3}\right) = -\frac{\pi}{3} \)
Since \(\tan\frac{\pi}{4} = 1\),
\( \displaystyle \tan^{-1}(1) = \frac{\pi}{4} \)
Adding:
\( \displaystyle -\frac{\pi}{3} + \frac{\pi}{4} = \frac{-4\pi + 3\pi}{12} = -\frac{\pi}{12} \)