| − | Inherent in the concept of infinity is the concept of infinitesimal: infinity small. [[Archimedes]] had used the idea to calculate the area under a parabola, and since the 17th century, mathematicians like [[Fermat]], [[Euler]], [[Newton], and [[Leibniz]] based their calculations of integrals and differentials on them. Only with the reformulation of calculus by [[Riemann]], [[Cauchy]], and others, they fell into disuse. | + | Inherent in the concept of infinity is the concept of infinitesimal: infinity small. [[Archimedes]] used small numbers and areas, as in calculating the area under a parabola, but the [[Ancient Greeks]] rejected the concept of infinity. Beginning with the 17th century, mathematicians like [[Fermat]], [[Euler]], [[Newton]], and [[Leibniz]] used the concept of infinitesimal in a primitive way in integrals and differentials on them. [[Bernhard Riemann]] used the concept of infinitesimal to develop a rigorous definition of the integral, now known as the [[Riemann Integral]]. |