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Advanced

The bell tolls

An equilateral triangle inscribed in a rectangle. What is its area X in terms of triangle areas A and B?

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Intermediate

Under the volcano

A square containing a right isosceles and an equilateral triangle. What’s the angle α?

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Intermediate

The Pisa experiment

Four squares and an altitude to the top vertex form a right yellow traingle. What is the proportion yellow : green?

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Intermediate

The queen

A cyclic quadrilateral with extended sides and two tangents forming an angle γ. What is γ in terms of α and β?

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Intermediate

Two hemispheres

A triangle with its circumscribed circle and a smaller intersecting circle. The two intersection points and the circumcentre are shown. What’s the proportion red : green?

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Intermediate

Boxed in

A square with an inscribed right triangle. What fraction is yellow?

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Intermediate

Napoleon strikes again

Three equilateral triangles and two line segments. Prove that the three red points are collinear.

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Intermediate

An equitable portion

A square, its diagonals and a right triangle. What fraction is green?

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Beginner

The leftward lean

Two triangles form a quadrilateral. What’s the total orange area?

Categories
Intermediate

Eternal snow

A triangle with two angle bisectors. What fraction of its area is green?