论文部分内容阅读
高中数学必修4江苏版,人教版,北师大版及其他各种版本都介绍了三倍角的正弦公式及余弦公式,然而对这两个三角公式的应用却介绍甚少,为丰富教学内容,开阔师生视野,本文精选部分习题,介绍其应用如下,供参考.一、三倍角的正、余弦公式求证:(1)sin3θ=3sinθ-4 sin~3θ;(2)cos3θ=4cos~3θ-3cosθ.证明(1)sin3θ=sin(2θ+θ)=sin2θcosθ+
High school mathematics compulsory 4 Jiangsu version, PEP, Beijing Normal University version and other versions have introduced the triple-angle sine and cosine formula, but the application of these two trigonometric formulas are poorly understood, in order to enrich the teaching content , Broaden the horizons of teachers and students, the selected part of the exercise of this article, describes its application as follows, for reference. First, triple the positive and cosine formula to prove: (1) sin3θ = 3sinθ-4 sin ~ 3θ; (2) cos3θ = 4cos ~ 3θ-3cosθ. Proof (1) sin3θ = sin (2θ + θ) = sin2θ cosθ +