Secant and tangent of a circle

From Karnataka Open Educational Resources
Jump to navigation Jump to search

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


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 ?