二、整体运用整体观察角的结构特征,将所求的三角函数值中的角,转化为所给角与特殊角的和与差的形式,实现由未知向已知的转化.例2 (1)已知https://bgk-photo.cdn.bcebos.com/960a304e251f95ca685d48d6d9177f3e67095222.jpg,求https://bgk-photo.cdn.bcebos.com/00e93901213fb80e0446bbb726d12f2eb938943f.jpg的值;(2)已知https://bgk-photo.cdn.bcebos.com/37d12f2eb9389b50ca683a329535e5dde7116e3f.jpg,又知https://bgk-photo.cdn.bcebos.com/8435e5dde71190effd6c48bfde1b9d16fdfa603f.jpg是第三象限角,求https://bgk-photo.cdn.bcebos.com/9345d688d43f87947557924ec21b0ef41bd53a22.jpg的值.分析:首先对所求三角函数与已知的三角函数中的角作比较,采用整体分析的方法,建立角与角之间的联系.因为https://bgk-photo.cdn.bcebos.com/3b292df5e0fe9925269bb33024a85edf8db1713f.jpg,https://bgk-photo.cdn.bcebos.com/80cb39dbb6fd52660d83e674bb18972bd4073622.jpg,https://bgk-photo.cdn.bcebos.com/574e9258d109b3de3b283e08dcbf6c81800a4c3f.jpg,https://bgk-photo.cdn.bcebos.com/d01373f082025aaf559aa4abebedab64034f1a22.jpg,所以,运用诱导公式可以将(1)、(2)两个小题顺利的解决.