Is there a decent online graph drawer

I'm looking for a graph drawer but most of them cannot draw what i want, like, x^2 + (y-1)^2 = 1. Do you know any decent one?

WolframAlpha does a fair job.

http://www.wolframalpha.com/input/?i=x%5…

. . . although the x and y scales are not always equal.
. . . if you miss the scale difference, an elipse might look like a circle
. . . and perpendicular lines might not appear so.

examples:
elipse;
http://www.wolframalpha.com/input/?i=x%5…
perpendicular lines:
http://www.wolframalpha.com/input/?i=y+%…

Graphing softwares will draw an equation like y = .....
here, use MS Excel.
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click : http://www.padowan.dk/graph/