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 2 added 36 characters in body

The fundamental theorem of calculus; all the long and difficult proofs of Eudoxus and Archimedes became clear and simple. Similarly with co-ordinate geometry.

show/hide this revision's text 1 [made Community Wiki]

The fundamental theorem of calculus; all the long and difficult proofs of Eudoxus and Archimedes became clear and simple.