An ellipse, two circles centred in its focal points, a chord and a tangent. What is the angle α?

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geometry puzzles

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- Post author By Rik
- Post date February 28, 2023
- No Comments on The lorgnette

An ellipse, two circles centred in its focal points, a chord and a tangent. What is the angle α?

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- Post author By Rik
- Post date December 14, 2022
- No Comments on Pushing the boundary

Two equilateral triangles are placed side by side. What’s the proportion green : red?

- Tags ellipse, length, proportion, triangle

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- Post author By Rik
- Post date November 10, 2022
- No Comments on The gyroscope

Two ellipses go through each others focal points. Prove that the focal points are the vertices of a parallelogram.

- Tags ellipse, parallelogram

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- Post author By Rik
- Post date July 19, 2022
- No Comments on The Pappus eggs

Three semicircles and a circle with their centres. Two orange ellipses with focal points in the semicircle centres (they share the middle one). Prove that their upper intersection point coincides with the circle centre.

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- Post author By Rik
- Post date May 11, 2022
- No Comments on The sliding ladder

A ladder seen from the side is sliding down a wall. Prove that a fixed point on the ladder traces part of an ellipse.