# 1.You will explain the definition of a circle, radius, chord, diameter, circumference and arc. 2.You will name and label the terms of a circle. 3.You will.

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1.You will explain the definition of a circle, radius, chord, diameter, circumference and arc. 2.You will name and label the terms of a circle. 3.You will understand special relationship between the diameter and the circumference. Lesson Objectives

TERMS OF A CIRCLE Developed by Ivan Seneviratne

A circle is a shape with all points in a plane at a fixed distance from the center. The given point is called the ‘CENTER’ of the circle. It is named by the center. The circle below is called circle A since the center is at point A. A What is a circle? Centre

Radius or Radii A ‘RADIUS’ of a circle is a segment that has one endpoint at the center of the circle and the other endpoint on the circle. The radius is referred to in formulas as r. A Radius

Chord A ‘CHORD’ of a circle is a segment that has its end points on the edge of the circle. A Radius Chord

Diameter A ‘DIAMETER’ of a circle is a chord that contains the center of the circle. It is referred to in formulas as d. A Radius Chord Diameter

Circumference The CIRCUMFERENCE (perimeter) is the distance around the circle and is referred to in formulas as C. To calculate the circumference of a circle you multiply pi with the diameter or pi with twice the radius. Circumference A Radius Chord Diameter

Arc An arc of a circle is a segment of the circumference of the circle. Radius Chord Major Arc Minor Arc

The Special Ratio If you measure the distance around a circle and divide it by the distance across the circle through the center, you will always come close to a particular value, depending upon the accuracy of your measurement. This value is approximately 3.14159265358979323846... We use the Greek letter (pronounced Pi) to represent this value. The number goes on forever. However, using computers, mathematicians have been able to calculate the value of to thousands of places.

Conclusion … the distance around the Circle… … its PERIMETER Diameter … the distance across the circle, passing through the centre of the circle Radius … the distance from the centre of the circle to any point on the circumference

This presentation is developed by Ivan Seneviratne © 2007, purely for personal use. ivanthexplorer@yahoo.co.uk

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