Well, the obvious thing to do is to take geodesic polar coordinates. Have you tried that? You should be able to prove that constant Gaussian curvature forces the metric to take a particular form, and this will in turn imply that geodesic circles have constant geodesic curvature.
– Zhen LinMay 11 '11 at 14:14
@Zhen Lin: Why is it not possible to simply/algebraically express geodesic curvature in terms of Gaussian curvature and $u_0 $? koletennbert's question has not yet been answered.
http://math.stackexchange.com/questions/162474/curvature-of-geodesic-circles-on-surface-with-constant-curvature?rq=1
– NarasimhamSep 25 '14 at 04:30