Crossed Ladder Theorm

Crossed Ladder Theorm

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In the crossed ladders problem, one of the important observations is that the height in the middle part can be found be the optic equation

1/h = 1/h_1 + 1/h_2

This observation can also be used in origami where to fold a paper into three equal pieces - the intersection of the diagonal of the full paper and the diagonal of the paper folded in half gives a third

╭──────╮
│            │
│            │
│            │
├──────┤
│            │
│            │
│            │
╰──────╯

1. https://mathworld.wolfram.com/CrossedLaddersTheorem.html