<a href="https://en.wikipedia.org/wiki/Kawasaki%27s_theorem" class="extiw" title="en:Kawasaki's theorem">Kawasaki's theorem</a>: a single-vertex crease pattern can be flat-folded if and only if the two alternating sets of angles around the crease have the same total angle.
<a href="//commons.wikimedia.org/wiki/User:David_Eppstein" class="mw-redirect" title="User:David Eppstein">David Eppstein</a>
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