Geometry

9

9.1 Introduction

In previous years, you learned about the geometry of points, lines and various polygons, made upfrom

lines. Here we will discuss the geometry of circle in a lot of depth.

See introductory video:VMhmc at http://www.everythingmaths.co.za

9.2 Circle Geometry

Terminology EMCBV

The following is a recapof terms that are regularly used when referring to circles.

arc An arc is a part of the circumference of a circle.

chord A chord is a straight line joining the ends of anarc.

radius A radius, r, is any straight line fromthe centre of the circle to a point on the circumference.

diameter A diameter,�, is a special chord thatpasses through the centre of the circle. A diameter is

the length of a straightline segment from onepoint on the circumference to another point on

the circumference, thatpasses through the centre of the circle.

segment A segment is the part of the circle that is cut offby a chord. A chord divides a circle into two

segments.

tangent A tangent is a line thatmakes contact with a circle at one point on the circumference. (AB is

a tangent to the circle atpoint P ) in Figure 9.1.

Axioms EMCBW

An axiom is an established or accepted principle. For this section, the following are accepted as

axioms.