Introduction
The Ancient Greeks knew something about integration. They did not have
our modern concept of function, were uneasy with limits, and they
certainly did not know about antiderivatives or fundamental theorems.
Nevertheless, Antiphon and Bryson calculated the area of a circle by filling it
up with a sequence of triangles. Archimedes did the same for the branch of a
parabola. Archimedes found the volume of a sphere by considering the areas
of circular cross sections and somehow adding them up. Eudoxus had previously
done the same for a cone. Archimedes calculated the surface area of
spheres as well. By any reasonable measure, that is integration.