# Lecture 17: Alexandrov's Theorem | Summary and Q&A

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August 26, 2014
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Lecture 17: Alexandrov's Theorem

## TL;DR

Folding polygons into polyhedra involves gluing the boundary to make a convex polyhedron, with various mathematical and algorithmic challenges.

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### Q: What is the main problem in folding polygons into polyhedra?

The main problem is determining whether a given polygon can be folded into a convex polyhedron.

### Q: How many rolling belts can you have in a single example?

In general, you can have more than one rolling belt, but four rolling belts is the maximum.

### Q: What does Alexandrov's Theorem state?

Alexandrov's Theorem states that given a convex polyhedral metric, there is a unique convex polyhedron that can be realized.

## Summary & Key Takeaways

• Folding polygons into polyhedra involves finding ways to glue the boundary of a given polygon to form a convex polyhedron.

• There are two main problems: the decision problem and the enumeration problem.

• Alexandrov's Theorem states that given a convex polyhedral metric, there is a unique convex polyhedra that can be realized.