搜狗做题网cos(π/17)*cos(2π/17)*cos(4π/17)*cos(8π/17)
cos(π/32)*cos(π/16)*cos(π/8)=
cos（－17/3π）＝?
求SINπ/64 COSπ/64 COSπ/32 COSπ/16 COSπ/8
已知cos（π4
【紧急求助】计算:cosα+cos(2π/3 +α)+cos（4π/3 +α）
已知sina=15/17,cosβ= - 5/13,a∈（π/2,π）,求cos（a+β）,cos（a-β）的值.
cos(π/4+x)=3/5,17π/12
cos(π/4+α）=3/5,17π
判断下列三角函数符号sin(-17/5派),cos(-23/4π),cos940°,cos-59/17π
cos sin π √
cos(-19/6π)
化简:cos(-π-α)