The aim of this paper is to show the use of mathematics in the development of information technologies. Although the contribution of mathematics in the development of various fields of informatics is not always recognized, its importance is emphasized. Understanding mathematical logic is important for the development of various information technologies. This paper presents only some of the examples of the application of mathematics in informatics. Mathematics is used in many areas, so it is not possible to list them all. The use of matrices and matrix transformations in digital photography processing is first described. The display of black and white, grey and colour photographs is explained, as well as the rotation and brightness change of the photograph. The RGB model is shown using the Cartesian system. Next, the importance of algorithms that originally derived from mathematics, but have great application in computer science, is emphasized. The complexity of the algorithms and the sorting and search algorithms that often use it are presented. Then follows the application of graph theory, and graphs, walks, cycles and trees are described. Graphs can be used to display a computer network, and trees to display and store data in a hierarchical relationship, and to display a decision tree. The use of information and coding theories to achieve communication is explained, and finally the importance of discrete mathematics and transformations is stated.