This document defines and describes different plane figures in geometry. It begins by defining a polygon as a closed polygonal line and its interior. It then discusses the elements of polygons, including sides and vertices. The document classifies polygons by the number of sides and describes triangles as polygons with three sides, three vertices, and three angles. It also discusses classifying triangles by their sides. The document defines a circumference as a closed curved line, while a circle is a plane figure bounded by a circumference. It notes that a circle has a center point that is equidistant from all points on the circumference, as well as radii and diameters.

1. UNIT 3
Plane FiguresPlane Figures
by Maria Adroverby Maria Adrover
CEIP S'ALGAR – PORTOCOLOM
Geometry 3rd_Unit 3_Plane figures

2. Polygon's definition
A polygon is a closed polygonal line and its inside.

3. Elements of a polygon

4. Types of polygon
● Polygons are classified depending to the
number of sides.

5. Triangle
● A triangle is a polygon with 3 sides, 3
vertexes and 3 angles.

6. Classifying triangles by sides

7. Circumference and Circle
● The circumference is a line while the circle is
a plane figure:
– The circumference is a close curved line.
– The circle is a plane figure limited by a
circumference.

8. Parts of a circle
● Center: It is exactly in the
middle. All the points of the
circumference are the same
distance to the center.
● Radius: The segment that
match the center with any
circumference point.
● Diameter: Segment that
match two circumference
points and cross the circle
center