The book is simple mathematics primarily for programmers, but not only. For programmers, the book gives the most necessary thing, without which it will be difficult for the programmer. The material is presented in the simplest and most correct presentation for immediate use by the programmer. The real application of mathematics by a programmer begins when he, having a task before him, himself, without an ensemble, guesses which branch of mathematics needs to be remembered for such a case, which specific method to take from it and how to program it. And all this himself, without outside help. The purpose of the book is not to teach programming mathematical algorithms. The goal is to take the problem and understand which mathematical algorithm to apply to it.