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摘要：两角和与差的正弦、余弦、正切公式： \(\cos (\alpha \pm \beta ) = \cos a\cos \beta \mp\sin \alpha \sin \beta\) \(\sin (\alpha \pm \beta ) = \sin \alpha \cos \beta \pm \c 阅读全文

摘要：https://baike.baidu.com/item/%E4%B8%89%E8%A7%92%E5%87%BD%E6%95%B0%E5%85%AC%E5%BC%8F/4374733 公式二 $\sin (\pi+\alpha ) = -\sin a$ $\cos (\pi+a) = -\cos a 阅读全文

摘要：\(\sin^{2}\alpha + \cos^{2}\alpha = 1\) \(\frac{\sin a}{\cos a} = \tan a\) 阅读全文