cos2x=1-2sin^2x 2sin^2x=1-cos2x 8sin^2x=4-4cos2x y=f(x)=(1+cos2x+8sin^2x)/sin2x =(1+cos2x+4-4cos2x)/sin2x =(5-3cos2x)/sin2x =(5-3cos2x)/√[1-(cos2x)^2] 已知00 ∴y>0 y*√[1-(cos2x)^2]=5-3cos2x y^2*[1-(...