百度作业网用最简单证这个恒等式sin(a+b)cos(a-b)=sinacosa+sinbcosb
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用最简单证这个恒等式sin(a+b)cos(a-b)=sinacosa+sinbcosb
sin(a+b)cos(a-b)
=(sinacosb+cosasinb)(cosacosb+sinasinb)
=sinacosa(cosb)^2+(cosa)^2sinbcosb+(sina)^2sinbcosb+sinacosa(sinb)^2
=sinacosa(cosb)^2+sinacosa(sinb)^2+(cosa)^2sinbcosb+(sina)^2sinbcosb
=sinacosa+sinbcosb
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=(sinacosb+cosasinb)(cosacosb+sinasinb)
=sinacosa(cosb)^2+(cosa)^2sinbcosb+(sina)^2sinbcosb+sinacosa(sinb)^2
=sinacosa(cosb)^2+sinacosa(sinb)^2+(cosa)^2sinbcosb+(sina)^2sinbcosb
=sinacosa+sinbcosb
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请点击下面的【选为满意回答】按钮,
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