sinπ/8*cos5π/8

sinπ/8*cos5π/8 sinπ/12cos5π/12等于 求cos5π/12sinπ/12 求值cos5π/8*cosπ8 sin(-π/7)和sin（-π/5）、cos4/7 π 、cos5/8 π 怎么算?如题! 为什么cos5π/12等于sinπ/12 cos5π/12=sinπ/12 怎么算的? sin(-4/3π）+cos5/6π= cos5分之π×cos5分之2π 求值:cos5π/8cosπ/8= 求值cos5π/8cosπ/8解cos5π/8cosπ/8,请写出过程. 计算cos5分之π+cos5分之2π+cos5分之3π+cos5分之4π cos5π等于= 计算cos5分之π+cos5分之2π+cos5分之3π+cos5分之4π cos5π的三角函数值, (sin5π/12+cos5π/12)(sinπ/12-cosπ/12) (sin5π/12-sinπ/12)(cos5π/12+cosπ/12)=? cos5/12πcosπ/12+cosπ/12sinπ/6=?