cos(派/5)*cos(2派/5)=?顺便教我一下,派怎么打,根号怎么打出来?

cos(派/5)*cos(2派/5)=?顺便教我一下,派怎么打,根号怎么打出来?
cos(派/5)*cos(2派/5)=?
顺便教我一下,派怎么打,根号怎么打出来?

cos(派/5)*cos(2派/5)=?顺便教我一下,派怎么打,根号怎么打出来?
原式=2sin(π/5)cos(π/5)cos(2π/5)/2sin(π/5)
=sin(2π/5)cos(2π/5)/2sin(π/5)
=2sin(2π/5)cos(2π/5)/4sin(π/5)
=sin(4π/5)/4sin(π/5)
=sin(π-π/5)/4sin(π/5)
=sin(π/5)/4sin(π/5)
=1/4
π,你就在这里复制吧
或者用搜狗输入法,输入pai,选3
根号√
先把输入法调为英文状态
然后按住Alt键
在右边小键盘输入41420即可