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   1. Convex and concave polygon

   A polygon is a closed plane figure made up of several line segments that are joined together.

    In the picture, there are two polygons: A and B.

    Every angle of the polygon A is less than or equal to 180°. It is called a convex polygon.

    The polygon B has an angle that is greater than 180°. It is called concave polygon.

    2. Types of polygons based on number of sides

    We have the following polygons: the triangle (three-sided polygon), the quadrilateral (four-sided polygon), the pentagon (five-sided polygon), the hexagon (six-sided polygon), heptagon (seven-sided polygon), the octagon (eight-sided polygon), the nonagon (nine-sided polygon) and the decagon (ten-sided polygon).

   Answer these questions:

   3. Irregular Polygons

    Note that the polygons F to K do not have all sides equal and all angles equal. These polygons are called irregular.

    Answer these questions:

    4. Regular Polygons

    A polygon with equal sides and angles is called regular.

    Answer these questions:

   5. Polygon parts

   Look at the polygon ABCDE! Each point is a vertex. In the picture, there are 5 vertices: A, B, C, D and C. The sides are the line segments that make up the polygon. In this case, we have 5 sides: AB, BC, CD, DE and EA.

    The diagonal is all line connecting two non consecutive vertices. In the picture, we can see that there are two diagonals per vertex. There are 5 diagonals: AC, AD, BD, BE and CE.

    Look at the picture and answer:

| Educational applications | Mathematics |
In Spanish  | Interactive

®Arturo Ramo García.-Record of intellectual property of Teruel (Spain) No 141, of 29-IX-1999
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