The document defines and classifies different plane shapes including polygons, triangles, quadrilaterals, and regular polygons. It discusses the key characteristics of these shapes such as the number of sides, angles, and parallel or equal sides. Specific shapes are defined, such as triangles being classified by angles (acute, right, or obtuse) and sides (equilateral, isosceles, or scalene). Quadrilaterals are classified as parallelograms, rectangles, rhombuses, trapezoids, or trapezoids. Regular polygons are those with all equal sides and angles.

1. GEOMETRY
Plane Shapes

2. POLIGONS
 Polygons are plane shapes enclosed in rectilinear
segments (their sides)
 Depending on the number of sides they have they
are called
triangles, quadrilaterals, pentagons etc…

3.  Triangle
3 sides.
 Quadrilateral
4 sides.
 Pentagon
5 sides.

4.  Hexagon
6 sides.
 Heptagon
7 sides.
 Octagon
8 sides.

5. LABELLING THE PARTS OF A TRIANGLE
 Vertex: Are indicated by capital
letters, A,B, C, etc.
 Sides: Can be AB, BC, CA, etc. or with
small letters a, b, c, etc. In the latter case
we use the letter of the opposite vertex.
 Angles: Are indicated by  etc.

6. TRIANGLES
Clasification by angles
 Two angles of a triangle will always be acute angles.
Depending on the other angle the triangle will be acute
angled, right angled, or obtuse angled.
obtuse acute right angled

7. TRIANGLES
Clasification by sides
 A triangle with all three sides equal is called an
equilateral. If it has two sides equal it is called
an isosceles. If the three sides are different it is
called a scalene.
scalene equilateral isosceles

8. QUADRILATERALS
CLASIFICATION OF QUADRILATERALS
PARALLELOGRAMS (OPPOSITE SIDES PARALLEL)
Rectangles Rhombuses Parallelograms
NON PARALLELOGRAMS
 Trapeziums Trapezoids
(only two sides parallel)

9. REGULAR POLYGONS
 A regular polygon is one in which all
sides are equal and all angles are equal.
 All regular polygons have a
circumscribed circumference.
 n = number of sides

10.  Triangle
3 sides.
 Quadrilateral
4 sides.
 Pentagon
5 sides.

11.  Hexagon
6 sides.
 Heptagon
7 sides.
 Octagon
8 sides.

12.  Enneagon or nonagon
9 sides.
 Decagon
10 sides.

13. CIRCUMFERENCE
 A circle is a shape with all points the same distance
from its center. A circle is named by its center. Thus, the
circle below will be called circle A since its center is at
point A.
 The circumference is the line which makes the circle.
 A circle is the most perfect plane figure.