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Kawasaki's Theorem

Geometry

Kawasaki's theorem, also called the Kawasaki-Justin theorem, is a result in the mathematics of paper folding that characterizes when a single-vertex crease pattern can be folded flat. It states that such a pattern is flat-foldable if and only if alternately adding and subtracting the angles between consecutive creases around the vertex produces a sum of zero. Crease patterns with more than one vertex do not follow this simple rule, and deciding whether they fold flat is an NP-hard problem.

Facts
Statement
A single-vertex crease pattern is flat-foldable if and only if the alternating sum of the angles of consecutive folds around the vertex is zero. 2
Classification
Statement Form
Characterization Theorem 1
Connections

Has Statement Form

In Branch

Source Kawasaki's theorem (Wikipedia)
Sources
1. Wikipedia: Kawasaki's theorem
WikipediaLead section, statement-form reference
Quote, Lead section, statement-form reference
It states that the pattern is flat-foldable if and only if alternatingly adding and subtracting the angles of consecutive folds around the vertex gives an alternating sum of zero.
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2. Kawasaki's theorem (Wikipedia)
  • Statement
    the pattern is flat-foldable if and only if alternatingly adding and subtracting the angles of consecutive folds around the vertex gives an alternating sum of zero.
  • In Branch: Discrete Geometry, Lead section
    Kawasaki-Justin theorem is a theorem in the mathematics of paper folding that describes the crease patterns with a single
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