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高中数学课本的各种版本都有如下两个优美的三角恒等式:(1)sinα+sinβ=2sinα+β2cosα-β2;(2)cosα+cosβ=2cosα+β2cosα-β2.若从正余弦函数的有界性来分析研究,则可得到如下两个三角不等式:
There are two beautiful triangle identities in high school math textbooks as follows: (1) sinα + sinβ = 2sinα + β2cosα-β2; (2) cosα + cosβ = 2cosα + β2cosα-β2. To analyze the world, you can get the following two triangular inequalities: