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.
Understand chords as elements of a circle
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
Download this geogebra file from this link.
Process (How to do the activity)
- 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