From Greek: okto "eight" + gonia "angle"
Adjust the octagon below by dragging any orange dot. By clicking on the top left command line,
you can switch it between a
Because an octagon has an even number of sides, in a
regular octagon, opposite sides are
Properties of regular octagons
Properties of all octagons
|Number of diagonals
||The number of distinct diagonals possible from all vertices. (In general ½n(n–3) ).
In the figure above, click on "show diagonals" to see them.
See Diagonals of a Polygon
|Number of triangles
||The number of triangles created by drawing the diagonals from a given vertex. (In general n–2).
In the figure above, click on "show triangles" to see them. See Triangles of a Polygon
|Sum of interior angles
||In general 180(n–2) degrees .
See Interior Angles of a Polygon
The Octagon Houses
Houses and rooms are sometimes built in an octagonal shape (pronounced: "ock-TAG-on-all"), perhaps because they
feel somewhat like a circular space but are made of straight wall sections which are easier to build.
While no longer so popular, there are examples that are being preserved as historic buildings.
The one on the right is the
Loren Andrus Octagon House in Washington, Michigan USA, built in 1860.
Because they are based on a regular octagon, opposite walls are parallel and the rooms have a pleasing symmetry.
Other polygon topics
Types of polygon
Area of various polygon types
Perimeter of various polygon types
Angles associated with polygons
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