求值域.①y=2sinxcos^2x/1+sinx②y=tan^2x-tanx+1/tan^2x+tanx+1

求值域.①y=2sinxcos^2x/1+sinx②y=tan^2x-tanx+1/tan^2x+tanx+1

①y=2sinxcos^2x(1-sinx)/(1+sinx)(1-sinx)=2sinx(1-sinx)然後配方得出y=-2[sinx+(1/2)]^2+(1/2)由影像知y∈[-4,1/2]②y=1-[2tanx/(tan^2x+tanx+1)]=1-{2/[tanx+(1/tanx)+1]}∵tanx+(1/tanx)≥2∴y∈[1/3,1)….