Determined by the center distance and the length of two radii,

The center distance is represented by d, and the radii of the two circles are represented by r and r respectively.

When d> is R+r, it is separated.

When d=R+r, it is circumscribed.

When r-r

When d=R-r, it is inscribed,

When 0 =

It can also be determined by the number of common points.

When two common points intersect, when one is common, it is tangent, and when there is no common point, it is separated or contained.