三角函数的化简、求值及三角恒等式的证明是三角变换的基本问题.解答三角变换题的策略通常是:观察角、函数运算间的差异,即进行所谓的“差异分析”.找出差异之间的内在联系,选择恰当的公式,促使差异的转化,从而达到三角函数“角度统一,名称统一”.但对于某些三角变换问题,若能紧紧 The simplification, evaluation of trigonometric functions and proof of trigonometric identities are the basic problems of trigonometric transformation. The strategies for answering trigonometric transformation are usually: the difference between observation angle and function operation, that is, the so-called “difference analysis”. The difference between the internal relations, select the appropriate formula to promote the transformation of differences, so as to achieve the trigonometric function “angle of unity, the name of unity. ” But for some triangular transformation, if it can be tight