Russian mathematician and geometer Nikolai Lobachevsky was born #OTD in 1792.
He is known primarily for his work on hyperbolic geometry, otherwise known as Lobachevskian geometry, and also for his fundamental study on Dirichlet integrals, known as the Lobachevsky integral formula.
Another of his achievements was developing a method for the approximation of the roots of algebraic equations (Lobachevsky method). via @wikipedia