Lambert's formula

tan(x)=x/(1-(x2)/(3-(x2)/(5-…)))

This structure, called the tangent, is effectively a tower of infinitely descending odd integers; Johann Heinrich Lambert used the tangent in 1761 to prove that pi is irrational. It results in steps approximating these curves. This fraction never ends. Accuracy increases with depth, a function of complexity. It defines the curve, but not the circle.