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sinα+cosα与sinαcosα常出现在各类三角问题中,解决这类问题的关键是灵活运用sinα+cosα与sinαcosα的关系.基本关系:(sinα+cosα)~2=1+2sinαcosα.基本作用:可用sinα+cosα表示sinαcosα;可用sinαcosα表示sinα+cosα.设sinα+cosα=t,则sinαcosα
sinα + cosα and sinαcosα often appear in all kinds of triangular problems. The key to solve these problems is to flexibly use the relationship between sinα + cosα and sinαcosα. The basic relationship is: (sinα + cosα) ~ 2 = 1 + 2sinαcosα. sinα + cosα that sinαcosα; available sinαcosα said sinα + cosα. Let sinα + cosα = t, then sinαcosα