Definition of

Incircle

polygon with incircle
The circle that fits the inside of a polygon. It must touch the midpoint of each side of the polygon.

Triangles, regular polygons and some other shapes have an incircle, but not all polygons.

The incircle's radius is also the "apothem" of the polygon.


Below is the incircle of a triangle (try dragging the points):
See: Apothem

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