Differential and integral calculus were independently developed at the end of the seventeenth century by Isaac Newton (1642–1727) and Gottfried Leibnitz (1646–1716). A curve’s slope at a certain location was determined using differential calculus, and the area under a curve was calculated using integral calculus. It turns out that there is an inverse relationship between the differential and integral calculus for a wide class of functions, meaning that a differentiable function can be derived up to a constant by integrating its derivative. Mathematicians started to understand during the seventeenth century that the very base of mathematical analysis was highly unstable and vaguely defined. This acted as a major barrier to study once geometric intuition was no longer sufficient.