y=sqr(2-4x^2) xE[0,5/2]这里，x^2E[0,25/4] -4x^2E[-25/4,0]2-4x^2E[-17/4,2]sqr(2-4x^2)E[0,根2] y^2=2-4x^24x^2=2-y^2 x=sqr(2-y^2) /2反函数：y=sqr(2-x^2) /2 xE[0,根2]
