A triangle has no diagonals. A square has two diagonals of equal length, which intersect at the center of the square. The ratio of a diagonal to a side is. A regular pentagon has five diagonals all of the same length.

How many diagonals does triangle have?

A triangle has zero diagonals. Diagonals must be created across vertices in a polygon, but the vertices must not be adjacent to one another.

Why is there no diagonal in a triangle?

Triangles don't have any diagonal since each vertex is adjacent to the other two. And, it's not the case with quadrilaterals because a quadrilateral will have two pairs of opposite vertices. So, quadrilaterals have 2 diagonals.