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4/sin3C=8/(sin2C+sinC)等于4/(3sinC-4sin³C)=8/(2sinCcosC+sinC)详细步骤
题目详情
4/sin3C=8/(sin2C+sinC)等于4/(3sinC-4sin³C)=8/(2sinCcosC+sinC)详细步骤
▼优质解答
答案和解析
sin3c=sin(2c+c)=sin2c*cosc+cos2c*sinc=2sinc*cos^2c+(1-2sin^2c)sinc=2sinc*(1-sin^2c)+sinc-2sin^3c=3sinc-4sin^3c
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