Secant and tangent of a circle

A tangent is a line touching a circle in one point. A secant is the line through two distinct points on a circle.

Objectives

To understand tangent and secant of a circle.

Estimated Time

30 minutes

Prerequisites/Instructions, prior preparations, if any

• The students should have a prior knowledge about a circle and its basic parts and terms.
• They should know the clear distinction between radius, diameter, chord, secant and tangent.

Materials/ Resources needed

• Digital : Computer, geogebra application, projector.
• Non digital : Worksheet and pencil, compass, strings
• Geogebra files : Lines in a circle.ggb 

Download this geogebra file from this link.

Process (How to do the activity)

• The teacher can show the geogebra file.
• Move the points on circumference and explain secant.
• When both endpoints of secant meet, it becomes a tangent.
• Name the points on the circumference of the circle.
• At how many points is the line touching the circle ?
• What is the line called ?

• Evaluation Questions

1. What is the difference between the secant and a tangent?
2. What is the difference between the chord and a secant ?
3. Can you draw a secant touching 3 points on the circle ?
4. At how many points does a tangent touch a circle ?
5. How many tangents can be drawn to a circle ?
6. How many tangents can be drawn to a circle at any one given point ?
7. How many parallel tangents can a circle have at the most ?