Secondary special education of the republic of uzbekistan

Integers.
Subtraction has not been introduced for the simple reason that it can be defined as the inverse of addition. Thus, the difference a − b of two numbers a and b is defined as a solution x of the equation b + x = a. If a number system is restricted to the natural numbers, differences need not always exist, but, if they do, the five basic laws of arithmetic, as already discussed, can be used to prove that they are unique. Furthermore, the laws of operations of addition and multiplication can be extended to apply to differences. The whole numbers (including zero) can be extended to include the solution of 1 + x = 0, that is, the number −1, as well as all products of the form −1 × n, in which n is a whole number. The extended collection of numbers is called the integers, of which the positive integers are the same as the natural numbers. The numbers that are newly introduced in this way are called negative integers.
Exponents
Just as a repeated sum a + a + ⋯ + a of k summands is written ka, so a repeated product a × a × ⋯ × a of k factors is written . The number k is called the exponent, and a the base of the power .
Modern precursors.
Integrals.
Johannes Kepler's work Stereometrica Doliorum published in 1615 formed the basis of integral calculus. Kepler developed a method to calculate the area of an ellipse by adding up the lengths of many radii drawn from a focus of the ellipse.
A significant work was a treatise, the origin being Kepler's methods,[20] published in 1635 by Bonaventura Cavalieri on his method of indivisibles. He argued that volumes and areas should be computed as the sums of the volumes and areas of infinitesimally thin cross-sections. He discovered Cavalieri's quadrature formula which gave the area under the curves xn of higher degree. This had previously been computed in a similar way for the parabola by Archimedes in The Method, but this treatise is believed to have been lost in the 13th century, and was only rediscovered in the early 20th century, and so would have been unknown to Cavalieri. Cavalieri's work was not well respected since his methods could lead to erroneous results, and the infinitesimal quantities he introduced were disreputable at first.
Torricelli extended Cavalieri's work to other curves such as the cycloid, and then the formula was generalized to fractional and negative powers by Wallis in 1656. In a 1659 treatise, Fermat is credited with an ingenious trick for evaluating the integral of any power function directly. Fermat also obtained a technique for finding the centers of gravity of various plane and solid figures, which influenced further work in quadrature.