COSπ/5乘以COS2π/5

COSπ/5乘以COS2π/5 cosπ/5 乘以cos2π/5等于多少 求COSπ/5*COS2π/5 cosπ/5×cos2π/5= cosπ/5×cos2π/5 cosπ/5cos2π/5 cosπ/5cos2π/5=? 计算cos∏/5乘以cos2∏/5的值. cosπ/5 - cos2π/5 怎样变成 cosπ/5 + cos2π/5rt cosπ/5乘以cos2π/5的值是多少?请给出具体解题过程,谢谢拜托各位大神 （cosπ/5）（cos2π/5)的值等于 cosπ/5·cos2π/5等于多少? cosπ/5*cos2π/5的值等于 化简cosπ/5cos2π/5RT. 若cos(π-θ)=3/5,cos2θ= cos(π-θ)=3/5 求cos2θ cos(π- θcos2θ)=3/5 求 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?