有些代数问题 ,当我们用代数方法解决时 ,会觉得束手无策 .如果通过三角代换把它们转化为三角问题 ,不仅可使题中各量之间的关系变得直接明了 ,结构特征显现 ,而且代数中原来繁琐、复杂的运算变成了简单、灵活多变的三角运算 .本文将探讨两类适合用三角代换法解决的代数问题 . Some algebraic problems, when we solve them with algebraic methods, feel helpless. If we convert them into trigonometric problems through trigonometric substitution, not only can the relations between the quantities in the questions become straightforward, the structural features appear, but also the algebras. The original cumbersome and complicated operation has become a simple, flexible trigonometric operation. This paper will discuss two types of algebraic problems that are suitable for trigonometric substitution.