在三角函数的学习中,加法定理占居主导地位,其中正、余弦的和角公式是最基本的,诱导公式、倍角公式、半角公式、和差化积、积化和差均可由它演绎而来.文[1]提出”建立以和角公式为纲的三角新体系”,并提出一些精简传统教材的建议,这是颇有见地的.关于加法定理的证明,一般教材都 In the study of trigonometric functions, the additive theorem dominates, and the sum and cosine sum formulas are the most basic. Induced formulae, double-angled formulas, half-width formulas, and differential products, productizations and differences can all be deduced from it. Lai Wen [1] proposed the establishment of a new triangular system based on the formula of He angle, and proposed some suggestions for streamlining traditional textbooks. This is quite insightful. With regard to the proof of the addition theorem, the general textbooks are