The role of foreign mathematics. The function part of foreign high school mathematics textbooks plays an important role in domestic high school mathematics textbooks. The content of function runs through foreign countries all the time, which is the main line of foreign high school mathematics courses. The United States, Britain, France and other European countries all study functions, so foreign mathematics studies functions. Functions include first-order functions, second-order functions, third-order functions, images, logarithmic functions, inverse proportional functions, exponential functions, trigonometric functions and their applications.