Abstract. This article provides a detailed description of trigonometric functions and the main operations performed on them. Trigonometric functions — sine, cosine, tangent, and cotangent — are one of the important branches of mathematics, expressing the relationship between angles and sides of a triangle. The article analyzes the definitions of these functions, their representation by the unit circle, and their main properties. It also examines the operations of addition, subtraction, multiplication, and division on trigonometric functions, identical transformations, and methods for using basic formulas. The process of mastering the topic is facilitated by practical examples. The widespread use of trigonometric functions in physics, engineering, astronomy, and other natural sciences is also emphasized. This article serves to strengthen students' trigonometric knowledge and develop problem-solving skills.