If $ \tan^{-1} x + \tan^{-1} y = \frac{4\pi}{5} $, then $ \cot^{-1} x + \cot^{-1} y $ is equal to-

Question

$ \pi $

$ \frac{\pi}{5} $

$ \frac{2\pi}{5} $

$ \frac{3\pi}{5} $

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