Abstract: The Pythagorean Theorem, perhaps the most widely known result in mathematics, has been proven in countless ways, and remains a basic building block of Euclidean geometry. Pythagorean Theorem analogs in non-Euclidean geometries can provide a gateway into understanding those geometries.

• 1. Introduction
• 2. The Plane Truth
• 3. Rounding Things Out
• 4a. Stretching the Truth (Poincaré Disk Model)
• 4b. Stretching the Truth (Hyperboloid Model)
• 5. Summary
• Bibliography
• Appendix: Discovering Pythagoras

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