> A1 := (2*y-y^2)^(1/2);
> A2 := -(2*y-y^2)^(1/2);
> B1 := (1-y^2)^(1/2);
> B2 := -(1-y^2)^(1/2);
> plot({A1, A2, B1, B2}, y=-1.00..2.00);
>