按照一般习惯,对三角恒等式的证明,我们都是从等号复杂的一端入手,经过一系列恒等变换,使它等于等号另一端,从而达到证明的目的。这是大家公认的一个重要规律与证明技巧。事物都是一分为二的,那么由较简单的一端入手,往较复杂的一端推证行不行?回答是肯定 In accordance with the general practice, for the proof of triangular identity, we start from the complicated end of the equal sign, and after a series of equal transformations, it is equal to the other end of the equal sign, so as to achieve the purpose of proof. This is an important law and proven skill that everyone recognizes. Things are divided into two, then starting from the simpler end, to the more complex end to push the line does not work? Answer is positive