The domain of the function $f(x) = \sin^{-1}\left(\frac{x^2 - 3x + 2}{x^2 + 2x + 7}\right)$ is\\ (1) $[1, \infty)$\\ (2) $(-1, 2]$\\ (3) $[-1, \infty)$\\ (4) $(-\infty, 2]$