Two congruent semicircles with their centres and a chord. Prove that the two red triangles are congruent as well.
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In the red
Category: Beginner
Three congruent squares share two vertices while the upper sides coincide. What’s red : blue?
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The bad haircut
The symmetrical figure bounded by 4 black semicircles is what Archimedes called the “salinon” or “salt cellar”. Show it has the same area as the green disc of the same height.
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The falling pillar
Three congruent rectangles on a line. What’s the angle α?
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The see-through triangle
A regular hexagon and an equilateral triangle share a vertex. What is red : blue?
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Guylines II
A square, two orthogonal axes and two angles. What’s the proportion α : β?
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Pac-Man pack
Four Pac-Men eat the corners of a square while four others stand guard. What fraction of the square is eaten?
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Le col bleu
A square with two line segments. What fraction is blue?
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Night mountain
A rectangle containing three line segments. What fraction is blue?
The red and green wedges subtend the same angle, there are two right angles, and the blue sides have the same length. What is the ratio of lengths of the green and red segments?