# Introduction to chords

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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

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:

• 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)

Use geogebra file: Introduction to chords

• 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
 Circle Diameter Chord Chord Length 1 1 2 3 4