MathOverflow will be down for maintenance for approximately 3 hours, starting Monday evening (06/24/2013) at approximately 9:00 PM Eastern time (UTC-4).
show/hide this revision's text 1 [made Community Wiki]

"The shortest path between two truths in the real domain passes through the complex domain." -- Jacques Hadamard

I guess he meant that often the best proof of a theorem about real numbers uses complex analysis.