A triangle has zero diagonals. Diagonals must be created across vertices in a polygon, but the vertices must not be adjacent to one another. A triangle has only adjacent vertices.
Continue ReadingA triangle is made up of three lines and three vertex points. Adjacent vertices are those which are not formed from the same line. All of the vertices in a triangle are adjacent to one another, so therefore, a triangle is not formed from any diagonal line segments.
The triangle is the only polygon without diagonals. A quadrilateral, for example, is made up of four lines and four vertex points. It is possible to draw two diagonals, from one non-adjacent vertex to the other, across the center of the quadrilateral.
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