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### Concave and Convex Polygons

```
Date: 08/13/2001 at 23:51:01
From: Jack
Subject: Convex and Concave

What's the difference between convex and concave polygons (or shapes
in general)?

Thank you very much.
```

```
Date: 08/14/2001 at 12:01:10
From: Doctor Peterson
Subject: Re: Convex and Concave

Hi, Jack.

A concave figure is one that has an indentation.

This can be stated precisely by considering all line segments joining
any two points in the interior of the figure. If the entire segment
always lies within the figure, then the figure is convex; but if you
can go on a straight line from one point in the interior to another
and pass outside of the boundary, then the figure is concave:

+---------------------+
/                       \
/                         \
/                           \
/                             \
/                        +      \
/                        /        \
+                        /          \
\                  +----------------+
\                  \ /
\                  \
\                / \
\              /   \
\            +     \
\                  \
+------------------+

- Doctor Peterson, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
Elementary Definitions
Elementary Geometry
Elementary Triangles and Other Polygons
Middle School Definitions
Middle School Geometry
Middle School Triangles and Other Polygons

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