# The longest chord passes through the centre of the circle

From Karnataka Open Educational Resources

Investigating the diameter is the longest chord of a circle.

### Objectives

To understand longest chord passes through the centre and it is the diameter

### 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 : Diameter is longest chord.ggb

Download this geogebra file from this link.

### Process (How to do the activity)

Use the geogebra file to show how diameter is the longest chord.

Move the points on the circle to show the changes in the triangle.

What is the condition with respect to sides for formation of a triangle. Sum of two sides is larger than the third side.

Compare the chord length with sum of two radii. When is the triangle reduced to a line segment.

What can you conclude about the chord? When is it the largest?