AB的中点O坐标是
xo=(xa+xb)/2=(5-1)/2=2
yo=(ya+yb)/2=(2+4)/2=3
R^2=(x0-xa)^2+(yo-ya)^2=(2-5)^2+(3-2)^2=10
所以圆方程是
(x-2)^2+(y-3)^2=10