f(x)=sin(π/2+x)cosx+sinxsin(3π+x)=cosxcosx+sinxsin(π+x)=（cosx)^2+sinx (-sinx)=（cosx)^2-(sinx)^2=cos2x该函数最小正周期=2π/2=π当x∈（-π/6,π/4}时,f(x)∈（0,1）^-^ OK 回答了哦 好好学习...