Given triangle 
, there are four lines simultaneously tangent to the incircle (with center 
) and the 
-excircle (with center 
). Of these, three correspond to the sidelines of the triangle, and the fourth is known as the 
-intangent (Kimberling 1998, p. 161), illustrated above.
The intangents intersect one another pairwise, and their points of intersection form the so-called intangents triangle.
