cosπ/5*cos2π/5 =(2sinπ/5*cosπ/5*cos2π/5)/(2sinπ/5) =(sin2π/5*cos2π/5)/(2sinπ/5) =(2sin2π/低2部咋算的?
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cosπ/5*cos2π/5=(2sinπ/5*cosπ/5*cos2π/5)/(2sinπ/5)=(sin2π/5*cos2π/5)/(2sinπ/5)=(2sin2π/低2部咋算的?cosπ/5*
cosπ/5*cos2π/5 =(2sinπ/5*cosπ/5*cos2π/5)/(2sinπ/5) =(sin2π/5*cos2π/5)/(2sinπ/5) =(2sin2π/低2部咋算的?
cosπ/5*cos2π/5 =(2sinπ/5*cosπ/5*cos2π/5)/(2sinπ/5) =(sin2π/5*cos2π/5)/(2sinπ/5) =(2sin2π/
低2部咋算的?
cosπ/5*cos2π/5 =(2sinπ/5*cosπ/5*cos2π/5)/(2sinπ/5) =(sin2π/5*cos2π/5)/(2sinπ/5) =(2sin2π/低2部咋算的?
倍角公式
sin2a=2sinacosa
所以2sinπ/5*cosπ/5=sin2π/5
cosπ/5×cos2π/5=
cosπ/5cos2π/5=?
求COSπ/5*COS2π/5
COSπ/5乘以COS2π/5
cosπ/5×cos2π/5
cosπ/5cos2π/5
若cos(π-θ)=3/5,cos2θ=
cos(π-θ)=3/5 求cos2θ
cos(π- θcos2θ)=3/5 求
cosπ/5 - cos2π/5 怎样变成 cosπ/5 + cos2π/5rt
cosπ/5*cos2π/5 =(2sinπ/5*cosπ/5*cos2π/5)/(2sinπ/5) =(sin2π/5*cos2π/5)/(2sinπ/5) =(2sin2π/低2部咋算的?
（cosπ/5）（cos2π/5)的值等于
cosπ/5·cos2π/5等于多少?
cosπ/5*cos2π/5的值等于
cosπ/5 乘以cos2π/5等于多少
化简cosπ/5cos2π/5RT.
已知cos(α-β)=-4/5cos(α+β)=5/13,且α-β∈(π/2,π),α+β∈(3π/2,2π),求cos2α和cos2β的值
已知cos（α‐β）＝－4／5,cos（α+β）=4／5,且α‐β∈（π／2,π）,α+β∈（3π／2,2π）求cos2α,cos2β