先化简 f（x）=sin（π-x）sin（π/2-x）+cos²x=1/2sin2x+cos²x=12/sin2x+(1+2cos2x)/2=1/2sin2x+1/2cos2x+1/2=√2/2sin(2x+π/4)+1/2(1) T=2π/2=π(2) X∈(-π/8,3π/8) 0