diagoanali
A diagonal is a line segment connecting two non-adjacent vertices of a polygon or polyhedron. In a polygon, a diagonal connects two vertices that do not share an edge. For instance, in a square, there are two diagonals, each connecting opposite corners. A triangle, having no non-adjacent vertices, has no diagonals. The number of diagonals in a polygon with n sides can be calculated using the formula n(n-3)/2. This formula arises from the fact that each vertex can connect to n-3 other vertices (excluding itself and its two adjacent vertices), and since each diagonal connects two vertices, we divide by two to avoid double-counting.
In three-dimensional geometry, a diagonal can also connect two vertices of a polyhedron that do not lie