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The letter box

A rectangle with a diameter and two inscribed squares. What is its area in terms of the square areas A and B?

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A close encounter

Two semicircles are tangent to each other’s diameter. Are the line segments connecting their corners parallel?

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The extra large

A triangle with a cevian splitting its base in parts of length 2 and 1. What is the angle α?

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The stuck boulder

A rectangle contains a circle wedged between two triangles. What is the circle radius in terms of triangle heights a and b?

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The Queen’s chamber

A right triangle with three squares forming a smaller inner triangle. What is the maximal blue fraction?

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The red planet

A semicircle with a chord and a line segment perpendicular to it. What is the total area in terms of lengths a and b?

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The Holy Trinity

Three similar triangles are placed such that they form a large triangle. What is the proportion of line segments a : b?

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Kindergarten

A circle with three tangents and two squares. The accentuated vertex is a tangency point. What’s the angle α?

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The earth projection

A circle touching a semicircle and a triangle. What is the proportion blue : green?

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Cordon sanitaire

Two perpendicular lines and a third line. Four circles are tangent to all three lines. Prove that their areas satisfy AB=CD.