“换元”的思想在整个数学中都是很重要的,本文只对三角换元法做必要的探讨.三角换元法多用于条件不等式的证明或一些函数值的计算,也可用于解决一些几何问题,即把某些代数问题或几何问题转化为三角问题,这就是代数问题或几何问题的三角解法,下面举例说明. The idea of ​​“changing yuan” is very important in the whole mathematics.This paper only makes necessary discussion on the triangle changing method.Coupled triangle method is mostly used in the proof of conditional inequalities or in the calculation of some function values, To solve some geometric problems, that is, to convert some algebraic problems or geometric problems into triangular problems, this is a triangular solution to algebraic problems or geometric problems, as illustrated below.