The radius of circle C is 1, which is tangent to the Y axis in the first quadrant. See the figure below. The x coordinate of the center is 1, and the y coordinate of the center is b.

So the circular equation is: (X- 1)? +(Y-b)？ = 1

Judgment: AB=√3, as shown in figure, 0

A=√(9/ 10)，B=√( 10/3)

Substituting X=A and Y=0 into the hypothetical cyclic equation, we get: b=0.9987.

The circle equation is: (X- 1)? +(Y-0.9987)？ = 1