The functions \(f\) and \(g\) have domains \((-1, \infty)\) and \((0, \infty)\) respectively and are defined by
$$f(x) = \cosh x, \qquad g(x) = x^2 - 1.$$
- State the domain and range of \(fg\). [2]
- Solve the equation \(fg(x) = 3\). Give your answer correct to three decimal places. [3]