Irrational number

Another Pythagorean of about the same date as Archytas was Theodorus of Cyrene, who is said to have proved geometrically that are incommensurable with unity. Theaetetus was one of his pupils.

— Irrational number

Michael Stifel... the greatest German algebraist of the sixteenth century... studied German and Italian works, and published in 1544, in Latin, a book entitled Arithmetica Integra. Melanchthon wrote a preface to it. Its three parts treat respectively of rational numbers, irrational numbers, and algebra.

— Irrational number