说明：  用于计算连续函数的逼近。 程序包含三种方法：用Legendre多项式作三次最佳平方逼近，用Tchebyshev多项式截断级数的办法以及使用插值余项极小化的方法。 代码清晰，注释简明，方便数值分析学习使用。
(It is used to calculate the approximation of continuous functions. There are three methods in the program: using Legendre polynomials for the third best square approximation, using Tchebyshev polynomials to truncate series, and using interpolation remainder to minimize. The code is clear and the annotation is concise, which is convenient for the study and use of numerical analysis.)