cosπ,cos关羽

sinx cosx tanx的特殊值 比例cos2π/3=1这样的
cosπ/4=?
cos7π/12=-sinπ/12=(√2-√6)/4
求值:cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11)
cosπ等于