A quadrilateral and a triangle. What’s the angle α?
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The boomerang
Tag: angle
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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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Baby steps
The edges of a cyclic quadrilateral extend to two intersections. O is the circle centre. The two diagonals intersect inside the circle. What is the angle α?
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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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Tip of the veil
A square with two right angles. What fraction is yellow?
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The crosshairs
A regular pentagon and two semicircles. Prove that they are orthogonal, i.e. the tangents in the intersection point are orthogonal.
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Three times three
A regular nonagon and two equilateral triangles. What’s the angle α?
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The laser game
In an equilateral triangular mirror room a laser is shot from the top vertex down to the base. The light ray bounces three times to return to the same base point. What is the angle α?
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The vanilla ice cream
A regular pentagon with two extended sides and a right angle. What is blue : green?
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The falling pillar
Three congruent rectangles on a line. What’s the angle α?