Introduction to chords

A chord is the interval joining two distinct points on a circle. This activity investigates formation of chord and compares with the diameter of the circle.

Objectives
Understand chords as elements of a circle

Estimated Time
30 minutes

Prerequisites/Instructions, prior preparations, if any
Prior knowledge of point, lines, angles, polygons

Materials/ Resources needed

 * Digital : Computer, geogebra	application, projector.
 * Non	digital : Worksheet	and pencil, compass, strings
 * Geogebra	files :  Introduction	to chords.ggb

Process (How to do the activity)
Hands-on work: Use geogebra file: Introduction to chords
 * Students to make a circle with thread/	string. Stick on a paper. The centre should be marked.
 * Mark points on the circumference of the	circle and measure the chord length.
 * Measure the longest chord length. What is	special about the longest chord? (Students should be able to say it	passes through the centre)
 * Mark any two points on the circumference of a circle, join the two	points. What is this line?
 * Establish	chord.
 * Move the slider	to show how the chord length varies. Ask students to observe the	changing chord lengths and when the chord length is maximum. Compare	chord length with diameter.


 * How many	parts is the circle divided	into by the chord? What do you notice about these two parts?
 * Establish	Segments.	When will the two segments	in a circle be equal?
 * Note	chord length for circles with different radius