...b,c.向量m=(2b-c,a),向量n=(cosC,cosA),m平行
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发布时间：2024-10-21 17:38
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热心网友
时间：2024-11-15 12:05
A=60°
(-2cos2C)/(1+tanC) +1
=-2[(cosC)^2-(sinC)^2]/(1+sinC/cosC)+1
=-cosC(cosC+sinC)*(cosC-sinC)/(cosC+sinC)+1
=2cosC(sinC-cosC)+1
=2sinCcosC-2(cosC)^2+1
=sin2C-cos2C
=√2sin(2C-45°）,
