# Angle Properties and Circle Theorem

Notes on Angle Properties and Circle Theorem

- Created by: E.H Jane
- Created on: 25-09-12 17:47

First 296 words of the document:

IGCSEMATHSGEOMETRY

Angle Properties and Circle Theorems

Line, Ray, Line Segment (Review):

Line: It does not have a definite length or an end point and can be extended in both directions. It is

represented by the symbol. Line AB is written as AB . It cannot be measured.

Ray : It does not have a definite length and has only one end point. It can be extended in one direction

only. It has a definite length. It is represented by the symbol . Ray AB is written as AB . It cannot be

measured.

Line Segment: It has two end points. None of the ends can be extended.

It is represented by the symbol

--.Line segment AB is written as AB . It can be measured.

Angle Properties of Regular Polygons:

A polygon is usually described as a closed two- dimensional shape bounded by straight lines. Examples

of polygon include triangles, pentagons, quadrilaterals etc.

A regular polygon has sides of equal length and all its angles are of equal size.

E.g. Square, Rectangle, Triangle etc.

The name of each polygon is derived from the number of angle it contains. The following list identifies

some of these polygons.

3 angles= triangle, 4 angles= tetragon, 5 angles= pentagon, 6 angles= hexagon, 7 angles= heptagon,

8 angles= octagon, 9 angles= nonagon, 10 angles= decagon, 12 angles= dodecagon.

The sum of interior angles of a polygon: A

A B E B

C D D C

From the vertex A of the following polygons, a line has been drawn to all other vertexes.

As you can see, the number of triangles is always two less than the number of sides.

There will be (n-2) triangles.

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