n * (n-3)/2
An 8 sided octagon belongs to the family of polygons
an polygon
An octagon
In most shapes the diagonals do not bisect one another. It might be possible to answer the question if it were more specific. To start with, shapes with how many sides?
All quadrilaterals (four sided shapes) have 2 diagonals.
number of diagonals = n(n-3)/2 n - number of sides of the polygon
The answer depends on their sizes! A small square will have a smaller area but a huge square will have a bigger area. Do the two shapes have equal sides, apothems, diagonals? Also, a square is a regular shape, what about the octagon?
An 8 sided octagon belongs to the family of polygons
Only a square and a rhombus will have all its diagonals bisecting vertices. In other shapes some - but not all - diagonals can bisect vertices.
triangle
an polygon
An octagon
In most shapes the diagonals do not bisect one another. It might be possible to answer the question if it were more specific. To start with, shapes with how many sides?
Triangle
All quadrilaterals (four sided shapes) have 2 diagonals.
not in all shapes.
The diagonals of a square and a rhombus cross at right angles.