1.
If f:R→[π3,π)f : \mathbb{R} \to [\frac{\pi}{3}, \pi) defined by f(x)=cos⁡−1(λ−x2x2+2)f(x) = \cos^{-1}\left(\frac{\lambda - x^2}{x^2 + 2}\right) is a surjective function, then the value of λ\lambda is equal to