CAIE IGCSE Mathematics Extended Circle Symmetry and Congruence

Practise using equal chords, equal tangents and radius properties to prove isosceles or congruent triangles in circle diagrams.

Syllabus
2028–2030
Topic
E4.8
Level
Extended

Exam points

  • use equal chords as equidistant from the centre, or reverse the property when justified
  • state that tangents from one external point are equal to prove an isosceles triangle
  • combine equal radii and right tangent angles to complete an SSS or RHS congruence proof

Covered syllabus points

E4.8.1 Use the following symmetry properties of circles: • equal chords are

E4.8 Circle theorems II question 1

[Maximum number: 3]
Figure for Question E4.8 Circle theorems II question 1 — CAIE IGCSE Mathematics Extended

NOT TO SCALE
A, B, C and D are points on the circle, centre O.
M is the midpoint of AB and N is the midpoint of CD.
O M=O N

Explain, giving reasons, why triangle OAB is congruent to triangle OCD.

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