A square containing another square with an extended side. What is tan(α) in terms of the red and green segment lengths?
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Baby block II
Author: Rik D. Tangerman
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Tilted hourglass III
A regular hexagon, a circle through its red centre and two line segments. What’s blue : orange?
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Primary colours
An equilateral triangle inside a rectangle. What is red : yellow : blue?
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The same vein
Two similar triangles ABC and EBD. Two line segments meet at point F. Prove that ABFC and EBDF are cyclic quadrilaterals.
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Equal rights
Two squares sharing a vertex. Two vertices are connected by a line segment. What is yellow : green?
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The boomerang
A quadrilateral and a triangle. What’s the angle α?
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The pentagon proportion
A regular pentagon and a circular arc through its red centre. What’s the proportion α : β?
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In touch
A regular nonagon and four equilateral triangles. The purple and yellow triangles share a vertex. Prove that the yellow triangles also share a vertex.
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The party hat II
An equilateral triangle with a circular arc through its red centre and two vertices. If the yellow area equals the green one, what’s the angle α?
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The lighthouse
A parallelogram and four equilateral triangles. What is yellow : green?