求值cos5π/8*cosπ8

求值cos5π/8*cosπ8 求值:cos5π/8cosπ/8= 求值cos5π/8cosπ/8解cos5π/8cosπ/8,请写出过程. 2倍角公式求值》cosπ/12 x cos5π/12 求值：(cosπ/8）^4+（cos3π/8）^4+(cos5π/8)^4+（cos7π/8）^4=正确答案是3/2,我想知道解题过程,自己解了很多遍都不对!谢谢! 求值:cosπ/7cos2π/7cos3π/7cos4π/7cos5π/7cos6π/7 RT,求值cosπ/11*cos2π/11*cos3π/11*cos4π/11*cos5π/11 用欧拉公式e^(ix)=cosx+isinx求值cosπ/7+cos3π/7+cos5π/7 sinπ/8*cos5π/8 tanπ/8+cosπ/8求值求值, cos（-8π/3）求值 cos（-8π/3）求值 cosπ/11×cos2π/11×cos3π/11×cos4π/11×cos5π/11=?求值cosπ/11×cos2π/11×cos3π/11×cos4π/11×cos5π/11=?求值 最后几步由sin6π/11×cos5π/11到sin10π/11怎样变得 cosπ/12*cos5π/12结果是1/4 cos5分之π×cos5分之2π 求值cosπ/11*cos2π/11*cos3π/11*cos4π/11*cos5π/11求详细过程和重要步骤的原因(1/4*sin8π/11*cos3π/11*cos5π/11)/2sinπ/11=(1/4*sin3π/11*cos3π/11*cos5π/11)/2sinπ/11这一步骤是怎么变过来的 8sin(π/32)cos(π/32)cos(π/16)cos(π/8),求值 计算不太明白...求值sin(-1320°）*cos1110°+cos（-1020°）sin750°+tan（-405°）求值sin25π/6+cos25π/3+tan25π/4+sin7π/3*cos13π/6-cos5π/3