Two coplanar circles are tangent to each other if they are tangent to the same line at the same point. Tangent circles may be tangent either internally or externally. Tangent circles are tangent internally if one lies in the interior of the other (except for the point of tangency).n the figure below, point P is the point of tangency. A common tangent is a line that is tangent to each of two coplanar circles. A common tangent can be tangent either internally or externally. A common internal tangent is a common tangent that intersects the segment that joins the center of the two circles.