Calculus is the study of 'Rates of Change'. Calculus as we know it today was developed in the later half of the seventeenth century by two mathematicians, Gottfried Leibniz and Isaac Newton. There are two main branches of calculus: Differential Calculus and Integral Calculus. Differential calculus determines the rate of change of a quantity, integral calculus finds the quantity where the rate of change is known. "Functions" are defined by a formula. Are you ready for Calculus?
