Let f and |f| belong to R*[a, ] for all > a. Show that f

Let f and |f| belong to R*[a, γ] for all γ > a. Show that f ∈ L[a, ∞] if and only if for every ε > 0 there exists K(ε) > a such that if q > p > K(ε) then ∫qp |f| < δ.