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Advanced

It’s all right

A regular pentagon with a diagonal and a right triangle. What’s the angle α?

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Intermediate

Uneven cups

Two semicircles and several line segments. Prove that the red line segments are parallel.

Categories
Intermediate

The glass splinter

A triangle of which two sides and one angle are given. What’s the angle α?

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Beginner

The triskelion

A circle containing an equilateral triangle and three squares. What fraction is purple?

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Advanced

The Christmas star

Two congruent concentric equilateral triangles. Prove that the gold fraction is red/blue.

Categories
Intermediate

The seesaw

A regular hexagon with three diagonals and two line segments at right angles. What is the proportion green : yellow : blue : orange?

Categories
Beginner

The consonant squares

Four squares and a rectangle. What’s the angle α?

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Intermediate

The Zamani suggestion

Two regular hexagons share a vertex. What’s the area proportion red : yellow hexagon?

Categories
Beginner

The forward lean

A square with a diagonal and an isosceles triangle. What fraction is brown?

Categories
Intermediate

The purple square

A regular octagon of side length 2 with two diagonals and a square. What is the purple area?