∫(1→∞) dx/[x(x² + 1)] dx 或 = lim(b→∞) ∫(1→b) dx/[x(x² + 1)]= ∫(1→∞) [(x² + 1) - x²]/[x(x² + 1)] dx= ∫(1→∞) [1/x - x/(x² + 1)] dx= ln(x) - (1/2)ln(x² + ...