三角恒等变换是三角函数和平面向量这两章的延续和发展,它是解决生产、科研等实际问题的工具,又是进一步学习其他相关知识的基础。变换是数学工具,也是数学学习的主要对象之一,三角变换与代数变换一样,只变形不变其质,它可以揭示那些外形不同但实质相同的三角函数式的变换。它无疑是高考必考的重点内容,在解题过程中注意灵活地加以运用。一、知角求值一般所给出的角都是非特殊角。当“已知角”有一个 Triangle constant transformation is the continuation and development of trigonometric functions and plane vectors. It is a tool to solve practical problems such as production and scientific research, and is the basis for further learning of other related knowledge. Transform is a mathematical tool, but also one of the main objects of mathematical learning. Triangular transformation, just like algebraic transformation, is only a transformative one. It can reveal transformations of trigonometric functions with different shapes but substantially the same features. It is undoubtedly the key content of the entrance exam must pay attention to the flexibility in the process of solving problems to be used. First, the value given to the general angle given are non-special angle. When “known angle ” has one