（cosπ/12 -sinπ/12）（cosπ/12 +sinπ/12）=

（cosπ/12 -sinπ/12）（cosπ/12 +sinπ/12）= （sinπ/24)(cosπ/24)(cosπ/12) （sinπ/24)(cosπ/24)(cosπ/12) sinπ/12*cosπ/12=? 求值：sin(π/12)+cos(π/12) sin(π/12)-cos(π/12)= cos*π/12—sin*π/12 cosπ／12乘以sinπ／12 计算cosπ/12*sinπ/12 已知α=7/12π,那么cosα√（1-sinα）/(1+sinα)+sinα√（1-cosα）/(1-cosα)= -（cos^2π/12-sin^2π/12)为什么等于-(cosα+π/12） （cosπ/12-sinπ/12)*(COSπ/12+sinπ/12)等于 (cosπ/12 -sinπ/12)(cosπ/12 +sinπ/12)等于 （cosπ/12-sinπ/12)(cosπ/12+sinπ/12)的值为 (sinπ/12+cosπ/12)(sinπ/12-cosπ/12)= cos^2π/12-sin^2π/12等于 sin(π/12)cos(π/12)的值 求sin π/12-(根号3)cos π/12