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In geometry, the tangential triangle of a triangle (other than a right triangle) is the triangle whose sides are on the tangent lines to 's circumcircle at its vertices. Thus the incircle of the tangential triangle coincides with the circumcircle of .
Note: A right triangle has no tangential triangle because the tangent lines to its circumcircle at its acute vertices are parallel, hence it cannot form the sides of a triangle.
- The reference triangle is the tangential triangle's contact triangle or Gergonne triangle.