Two functions g and h are defined on the set R of real numbers by \(g : x \to x^{2} - 2\) and \(h : x \to \frac{1}{x + 2}\). Find : 

(a) \(h^{-1}\), the inverse of h ;

(b) \(g \circ h\), when \(x = -\frac{1}{2}\).