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Activity Overview

Students explore the concept of 'centre' using a range of familiar shapes. The dynamic geometry environment on TI-Nspire is then used to construct a triangle. Using the perpendicular bisector tool students locate the circumcentre of the triangle then use congruent triangles to establish a proof.


  • ACMMG243– Formulate proofs involving congruent triangles and angle properties
  • ACMMG201– Develop the conditions for congruence of triangles


  • Perpendicular
  • Bisector
  • Vertex
  • Congruent
  • S.A.S - Congruency Condition
  • Reflection
  • Transformation

About the Lesson

Students explore the concept of centre through a variety of shapes visually, dynamically and through paper folding. Students then use the TI-Nspire Geometry Application to construct a dynamic representation of the circumcentre of a triangle followed by a proof.