Angles in a circle subtended by a chord
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The angle made at the centre of a circle by the radii at the end points of a chord is called the central angle or angle subtended by a chord at the centre.
Objectives
Understand different angles subtended by a chord in 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 : Angle subtended by chord.ggb
Download this geogebra file from this link.
Process (How to do the activity)
- Two equal chords are drawn, the endpoints are joined to the center of the circle to form triangles.
- What can you say of the angles subtended by the two chords? How are the two subtended angles equal. Compare triangles formed.
- When is the subtended angle the largest?
- If the angles subtended are equal will the chords be of equal measure?
HW Activity : Draw circle, at the center draw two angles of equal measure. Mark the chords formed by the angles. Measure the lengths of the two chords. Note your observations.