cosπ/12=

cosπ/12= cos(π/12)cos(5π/12)= cos(π/32)*cos(π/16)*cos(π/8)= sinπ/12*cosπ/12=? sin(π/12)-cos(π/12)= cos(-π/12)过程 （cosπ/12 -sinπ/12）（cosπ/12 +sinπ/12）= (sinπ/12+cosπ/12)(sinπ/12-cosπ/12)= cos5/12πcosπ/12+cosπ/12sinπ/6=? 若x=π/12,则cos(2x-π)*cos[2(x-π)]=? 化简函数y=cos^2(x+7π/12)-cos^2(x+π/12), 已知cos(a-b)=-12/13 cos(a+b)=12/13且π/2 （sinπ/24)(cosπ/24)(cosπ/12) （sinπ/24)(cosπ/24)(cosπ/12) 化简cos（π/12）*cos（5π/12） cos (π/12) × cos(5×π/12)的值 化简cos(π/4-a)cos(π/4+a)= 化简cos(1-π)+cos(3π+1)=