f(x)=2sin(π-x)cox
=2sinxcosx
=sin2x
x∈[-π/6,π/2],2x∈[-π/3,π]
f(x)max=f(π/4)=1
f(x)min=f(-π/6)=-√3/2π/4和-π/6怎么求的f(x) =sin2x最大值就是1 此时x=π/4 f(x)在[-π/6,0]为增函数且f(x)<0 f(x)在[0,π/2]有 f(x)>0 最小值就是f(-π/6)=-√3/2