Theodorus of Cyrene (Ancient Greek: Θεόδωρος ὁ Κυρηναῖος, romanized: Theódōros ho Kyrēnaîos; fl. c. 450 BC) was an ancient Greek mathematician. The only first-hand accounts of him that survive are in three of Plato's dialogues: the Theaetetus, the Sophist, and the Statesman. In the first dialogue, he posits a mathematical construction now known as the Spiral of Theodorus.
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