Counterintuitive Intersection of Two Line Segments

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Two towers of heights and are separated by a distance . From the top of each tower, a light beam is aimed at the base of the opposite tower. This Demonstration shows that the height of the intersection (red dot) of the two light rays does not depend on the distance separating the two towers. This result is sometimes called the "crossed ladders theorem".

Contributed by: Bernard Vuilleumier (January 2023)
Open content licensed under CC BY-NC-SA



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