\(\tan^{-1}\left(\tan\frac{3\pi}{4}\right)=tan^{-1}\left(\tan\left(\pi-\frac{\pi}{4}\right)\right)\)
[Formula: tan(π – x) = -tan (x) , as tan is negative in the second quadrant. ]
\(=\tan^{-1}\left(-\tan\frac{\pi}{4}\right)\)
[Formula: tan -1(tan x) = x ]
=\(-\frac{\pi}{4}\)
