In the first what is the calculus? Before defining the calculus we can divide it into two categories; the first is differentiation, but the second is the integration. The differentiation: that category relates with the rate of change and the slope of the graphs, whereas we use the limits in finding the derivative of any curve: -The integration: that category relates with the area under and between the graphs, whereas appeared many theorems like Riemann integration, Monte Carlo integration and the fundamental theorem of calculus. -The differentiation is connected with integration by The fundamental theorem of calculus that tells us that: -The differential calculus and integral calculus is well-connected by many thing and from the new things that the derivative of a function can be found by knowing the integral of the inverse function to the derivative function, and that can be understood from the following equation: -The previous equation told us that: 1-we can find the derivative of any curve without taking the limits. 2-That equation is an good evidence for the strong connection between the differentiation and integration.