Composition (fog)(x) = f(g(x)): apply g first, then f. Domain of fog consists of all x in the domain of g such that g(x) lies in the domain of f. Composition is associative: (fog)oh = fo(goh), but NOT commutative: fog ≠ gof in general. If fog is injective, then g is injective. If fog is surjective, then f is surjective. The inverse function f^(-1) exists only when f is bijective. To find f^(-1): write y = f(x), solve for x in terms of y, then replace y with x. Properties: f^(-1)(f(x)) = x and f(f^(-1)(y)) = y. The graph of f^(-1) is the reflection of f's graph across y = x.