1-2sin^(45度+x)=cos(90°+2x)=sin2xf(x)=√3cos2x+sin2x=2sin(2x+60°)代入x[30,90] 2x+60°∈[120,240] sin(2x+60°)∈[√3/2,-√3/2]f(x)最大值=√3；x=30°,x[30,90] ，单调减
lz我算错了
