Decagon (10-gon)
Definition: A
polygon with 10 sides
Try this
Adjust the decagon below by dragging any orange dot. By clicking on the top left command line,
you can switch it between a
regular and
irregular decagon.
Properties of regular decagons
Interior angle
144°
Like any regular polygon, to find the interior angle we use the formula
(180n–360)/n . For a decagon, n=10.
See
Interior Angles of a Polygon
Exterior Angle
36°
To find the exterior angle of a regular decagon, we use the fact that the exterior angle
forms a
linear pair
with the interior angle, so in general it is given by the formula
180-interior angle.
See
Exterior Angles of a Polygon
Properties of all decagons
Number of diagonals
35
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
8
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
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