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高中数学代数第一册第三章3·4节“关于三角函数和(差)与积的互化”教学,对于求三角函数值、化简三角函数及三角函数式恒等变形具有重要的作用,由于公式繁多记忆不便,给教学带来不少困难,原因之一就是缺乏一个多样而统一的简单的公式所致。下面我们来提出一种解决问题,使八个公式统一起来的方案。首先,建立一个基本公式:cos(α+β)+cos(α-β)=2cosαcosβ
In the third chapter of the mathematics algebra of the senior high school, the teaching of the trigonometric function and the (difference) and product mutualization" in the first volume of the third chapter of the mathematics algebra has important effects on the trigonometric function value, the simplified trigonometric function, and the trigonometric constant deformation. Due to the inconvenience of formulas and the inconvenience of memory, one of the reasons for the difficulties in teaching is the lack of a diverse and unified simple formula. Let us propose a solution to solve the problem and unify the eight formulas. First, establish a basic formula: cos(α+β)+cos(α-β)=2cosαcosβ