Circular Reasoning: Who First Proved That C Divided by d Is a Constant?
The College Mathematics Journal
We argue that Archimedes proved that the ratio of the circumference of a circle to its diameter is a constant independent of the circle and that the circumference constant equals the area constant. He stated neither result explicitly (in surviving material), but both are implied by his work. His proof required the addition of two axioms beyond those in Euclid's Elements.
Richeson, David. "Circular Reasoning: Who First Proved That C Divided by d Is a Constant?" The College Mathematics Journal 46, no. 3 (2015): 162-171. https://www.tandfonline.com/doi/abs/10.4169/college.math.j.46.3.162