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Topic

Circles

8 entries in this archive currently use this topic.

Solution onlyDifficulty 6/10

A Solution to Crux Mathematicorum Problem 5021

A direct-similarity generalization proved with Pappus's theorem and a radical axis, presented without reproducing the original problem statement.

  • Projective geometry
  • Circles
  • Transformations
10 August 2026Read →
Solution onlyDifficulty 5/10

A Solution to Crux Mathematicorum Problem 5031

A concise incircle-inversion proof using contact-chord midpoints and a cyclic quadrilateral, presented without reproducing the original problem statement.

  • Triangle geometry
  • Circles
  • Transformations
10 August 2026Read →
Solution onlyDifficulty 6/10

A Solution to Crux Mathematicorum Problem 5088

A concise angle-chasing proof through tangency and cyclic quadrilaterals, presented without reproducing the original problem statement.

  • Circles
  • Triangle geometry
10 August 2026Read →
Solution onlyDifficulty 6/10

A Solution to Crux Mathematicorum Problem 5098

A unit-circle complex proof that reduces two geometric conditions to the same algebraic equation, presented without reproducing the original problem statement.

  • Triangle geometry
  • Circles
  • Algebra
10 August 2026Read →
Diagram

Pappus and Radical Axis for Problem 5021

The Pappus configuration and two circumcircles used in the generalized solution to Crux Mathematicorum Problem 5021.

  • Projective geometry
  • Circles
  • Transformations
10 August 2026Read →
Diagram

Incircle Inversion for Problem 5031

The incircle, its contact points, and the auxiliary intersections used in the inversion solution to Crux Mathematicorum Problem 5031.

  • Triangle geometry
  • Circles
  • Transformations
10 August 2026Read →
Diagram

Tangent Circle in a Parallelogram

The tangent circle, perpendicular feet, and cyclic configurations used in the solution to Crux Mathematicorum Problem 5088.

  • Circles
  • Triangle geometry
10 August 2026Read →
Diagram

Cyclic Orthocenter Configuration

A cyclic quadrilateral, two altitude feet, and an orthocenter in the configuration used for the solution to Crux Mathematicorum Problem 5098.

  • Triangle geometry
  • Circles
10 August 2026Read →

ELEMENTARY GEOMETRY

Problems, Proofs, and Diagrams

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English edition · 2026