1.y=-sinxcosx-[(cosx)^2-(sinx)^2] =-(1/2)sin2x-cos2x =-((√5)/2)sin(2x+θ)最小值为-((√5)/2)2.sinx+(sinx)^2=1=(sinx)^2+(cosx)^2 (cosx)^2=sinx (cosx)^2+(cosx)^4=sinx+(sinx)^2=1
