cos²5π/12+cos²π/12+5π/12+cos5π/12×cosπ/12
问题描述：
cos²5π/12+cos²π/12+5π/12+cos5π/12×cosπ/12
答
cos²5π/12+cos²(π/12+5π/12)+cos5π/12×cosπ/12=cos²(3π/12+2π/12)+cos²π/2+cos(3π/12+2π/12)×cos(3π/12-2π/12)=cos²(π/4+π/6)+cos(π/4+π/6)×cos(π/4-π/6)=co...