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Advanced

Ruyles squares

There are four possible squares with a vertex at distance a from the centre and two vertices on the circle of radius r. Find their areas in terms of a and r.

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Intermediate

Pushing the boundary

Two equilateral triangles are placed side by side. What’s the proportion green : red?

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Intermediate

The Pyramid of Austerlitz

An equilateral triangle and a parabola that is tangent to two of its sides in two vertices. Proof that the triangle centre coincides with the parabola focus.

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Beginner

The skewed tree

A triangle with a line segment through its centroid and parallel to a side. What faction is dark green?

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Intermediate

A deep connection

Two squares inside a circle. What is the circle area in terms of length a?

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Advanced

Square one

Three squares share a vertex. Two line segments pass through side midpoints. Prove that a : b = c : d.

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Intermediate

To shy away

Two squares share a vertex. What’s the proportion orange : blue?

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Intermediate

The domino effect

Two overlapping congruent rectangles. What’s the angle α?

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Beginner

Squaring a rectangle

A regular hexagon, a square and a rectangle. What is the area proportion rectangle : square?

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Intermediate

A clear vision

A circle containing a regular pentagon and two equilateral triangles. All shown points are on the circle. What’s the angle α?