Incircle and excircles of a triangle polygon with any number of sides that has an inscribed circle—one that is tangent to each side—is called a tangential polygon. Incircle and excircles of a triangle In geometry, the incircle or inscribed circle of a triangle is the largest circle contained in the triangle; it touches (is tangent to) the three sides. The center of the incircle is a triangle center called the triangle's incenter. An excircle or escribed circle of the triangle is a circle lying outside the triangle, tangent to one of its sides and tangent to the extensions of the other two. Every triangle has three
Line (geometry) to that relationship. For instance, with respect to a conic (a circle, ellipse, parabola, or hyperbola), lines can be: In the context of determining parallelism in Euclidean geometry, a transversal is a line that intersects two other lines that may or not be parallel to each other. For more general algebraic curves, lines could also be: With respect to triangles we have: For a convex quadrilateral with at most two parallel sides, the Newton line is the line that connects the midpoints of the two diagonals. For a hexagon with vertices lying on a conic we have the Pascal line