EntityQ478728· pop 17· linked from 21 articlespedal triangleSign in to savetriangleConnectionsincircle and excircles of a triangleEntityorthocenterEntitycircumscribed circle for triangleEntitytriangleEntityInternational Standard Book NumberEntitypointEntityEuclidean geometryEntityOCLC, Inc.EntityperpendicularityEntitycyclic quadrilateralEntityhomothetic transformationEntitySimson lineEntityisogonal conjugateEntityincenterEntitytrilinear coordinatesEntityacute or obtuse triangleEntitymedial triangleEntityline–line intersectionEntityCarnot's theorem (perpendiculars)Entityhomothetic centerEntityCategoriesObjects defined for a triangle