A square is divided in several triangles and quadrilaterals. What is yellow : red?
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Spotlight II
Month: May 2024
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Video: Cramped space
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Circle a ranch brand
Connect 4 (blue) points B, C, D, E on a circle to some of the (orange) midpoints of non-adjacent arcs. (For example, C connects to J, E connects to L.) Intersect CJ with EL to get F, and intersect DK with BL to get G. Show that FG || JK.
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Secured package
A square with several line segments. Prove that the red line segments are parallel.
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Video: The red dot
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The drinking bird
Two circles with two radii and two tangents. The blue line passes through points of tangency and the circle intersection. Prove that α=β.
Puzzle author: David Odell.
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Circle crossings
The segment CD is tangent to the green circle c, ending on the orange circle d, which also contains the foot of the perpendicular line from C to the diameter of c which extends to D. What is the angle between the two circles?
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Video: Four five
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The leaning diamond
A square with two equilateral triangles. What’s the angle α?
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