Find the value of: tan⁻¹ (x/y) + tan⁻¹ ((y-x)/(y+x))

$\tan^{-1}\left(\frac{x}{y}\right) + \tan^{-1}\left(\frac{y-x}{y+x}\right) = \tan^{-1}\left(\frac{x}{y}\right) + \tan^{-1}\left(\frac{1 - \frac{x}{y}}{1 + \frac{x}{y}}\right)$ $= \tan^{-1}\left(\frac{x}{y}\right) + \tan^{-1}(1) - \tan^{-1}\left(\frac{x}{y}\right)$ $= \tan^{-1}(1) = \frac{\pi}{4}$