The book is available to a wide range of readers: students of universities, teachers and pedagogical institutes, teachers and students of secondary schools, technical schools, pedagogical schools and just lovers of mathematics. Understanding the first three chapters of it requires only knowledge of the school course of algebra and elements of trigonometry. Only the fourth, very short, chapter requires the most modest information from integral calculus. This information can be gleaned from any mathematical analysis textbook. However, without the fourth chapter, the work would have been unfinished. Individual chapters of the book have independent meaning and can be read independently of one another.