### unaccurate plot of a circle

Hi!

I want to plot a circle centered at the origin and radius sqrt(2). When I type:

plot(sqrt(2-x^2),-sqrt(2),sqrt(2),aspect_ratio=1)+plot(-sqrt(2-x^2),-sqrt(2),sqrt(2))

in sage 5.4, the graph obtained is really unaccurated.

However, for the circle of radius sqrt(3) works fine. Does anybody know why?

Of course I know there are several ways to plot a circle, but i want do do like this for showing my pupils some applications of integral calculus.

I think it is important to have a "plot" command working properly, since it is extensively used in teaching.