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正余弦函数的三倍角公式作为一个证明题出现在人教A版必修4习题3.1的B组中.尽管如此,由于平时运用公式解决问题的机会不多,学生对三倍角公式还是比较陌生的,有些问题也联想不到三倍角公式上去.但是三倍角公式却是许多试题的题源,受到高校自主招生和各类竞赛命题者的青睐.针对这种情况,笔者举例来简单谈谈公式的常见应用,以飨读者.一、熟悉公式容易证明三倍角公式:sin 3x=3sin x-4sin~3x;
The triple-angle formula for the cosine and cosine functions appears as a proving problem in Group B of the PEP 4 Quest 3.1 for Problem A, but nevertheless students are often unfamiliar with the triple-angle formula due to their limited chance of solving problems with formulas, Some problems also can not think of the triple angle formula up, but the triple angle formula is the source of many questions, subject to college self-enrollment and various types of competition propositions favor .In response to this situation, the author for example to briefly talk about the common formula applications , To 飨 readers. First, familiar with the formula easy to prove the triple angle formula: sin 3x = 3sin x-4sin ~ 3x;