Theodorus of Cyrene (the mathematician)

Theodorus of Cyrene was an ancient Greek mathematician known for his contributions to the understanding of irrational numbers, particularly those related to square roots. He is best known for proving that the square roots of non-square numbers, like 2, 3, and 5, cannot be expressed as fractions—meaning they are irrational. Theodorus is also attributed with presenting a geometric method for calculating these square roots. His work laid important groundwork for later mathematicians, influencing the development of number theory and geometry. He lived around the 5th century BCE and was often associated with the philosopher Plato.