(1)If a curve is symmetrical about the origin, then it is symmetrical about both axes.
(2)If a curve is symmetrical about both the axes, then it is symmetrical about the origin.
(3)A curve f(x,y)=0 is symmetrical about the line y=x if f(x,y)=f(y,x).
(4)For the curve f(x,y)=0, if f(x,y)=f(-y,-x),then it is symmetrical about the origin.
