前两项展开化简或者和差化积
后一项用降次公式
f(x)=2sinwx cosπ/6-1-coswx
=2(sinwx cosπ/6- coswx sinπ/6)-1
=2sin(wx-π/6)-1
f max=1,f min=-3
值域[-3,1]
f(x)=2sin(2x-π/6)-1
kπ+π/2=2x-π/6
2x= kπ+2π/3
对称轴方程x= kπ/2+π/3,k∈Z