lemniscate of Bernoulli

…of the rectification of the lemniscate, a ribbon-shaped curve discovered by Jakob Bernoulli in 1694, Giulio Carlo Fagnano (1682–1766) introduced ingenious analytic transformations that laid the foundation for the theory of elliptic integrals. Nikolaus I Bernoulli (1687–1759), the nephew of Johann and Jakob, proved the equality of mixed second-order partial…