作业帮1/2-cos^2(π/12)
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1/2-cos^2(π/12)
1/2-cos^2(π/12)
1/2-cos^2(π/12)
1/2-cos²(π/12)=1/2-cos²(π/12)
=[1-2cos²(π/12)]/2
=[cos(π/6)]/2
=[√3/2]/2
=√3/4
1/2-cos^2(π/12)
2cos平方π/12-1
计算cos平方π/12-1/2
根号(1-cosθ/1+cosθ)+根号（1+cosθ/1-cosθ)θ属于（π/2,π）
为什么cos(n-1)π=cos(n+1)πcos(n-1)π=cos(n-1+2)π=cos(n+1)π 对吗?
计算：cos（π/5)+cos（2π/5)+cos(3π/5)+cos(4π/5)
cos(π/17)*cos(2π/17)*cos(4π/17)*cos(8π/17)
cos^2α+cos^2(α+π/3)-cosαcos(α+π/3)化简
cos x>-1/2
证明cos 2x cos x=1/2(cos x+cos 3x)
cos^1度+cos^2度+cos^3度+……+cos^180度=?
cosπ/12-isinπ/12的模求cosπ/12-isinπ/12的模A 1 B√2 C -1 D cosπ/12
由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a)
求下列各式的值:(1)cos(-165°) (2)cos(7π/12) (3)cos(-61π/12) 求详解
求值:cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11)
求值：cos(π/11)-cos(2π/11)+cos(3π/11)-cos(4π/11)+cos(5π/11)
cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11)
cos²1+cos²2+cos²1°+cos²2°+.+cos²89°