Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In geometry, the circle of antisimilitude (also known as mid-circle) of two circles and is a circle for which and are inverses of each other. If and are non-intersecting or tangent, there exists one circle of antisimilitude; if and intersect at two points, there exist two circles of antisimilitude. When and are congruent, the circle of antisimilitude is degenerate; it becomes a line of symmetry, in which and are reflections of each other.