f(x)=(sinx+cosx)²+2cos²x-2=(sinx)^2+(cosx)^2+2sinxcosx+2cos²x-1-1=2sinxcosx+2cos²x-1=sin2x+cos2x=√2sin(2x+pai/4)2x+pai/4=2pai,x=7pai/8最小正周期是7pai/8x∈[π/4,3π/4]时,2x+pai/4...