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Joseph Louis Lagrange (1736-1813)

Born in France.
He applied mathematical analysis toprinciples estalished by Sir Isaac Newton to problems of astronomy.
He presided over the commission that introduced the metric system in 1793.
Antoine de Laloubère (1600-1664)

Born in France.
He was the first mathematician to study the properties of the helix.
Pierre Simon Laplace (1749-1827)

Born in France.
He developed the theory of probability.
Henri Léon Lebesgue (1875-1941)

Born in France.
He developed a new theory, known as the Lesbesgue integral theory.
He made contributions to set theory, the calculus of variations, and function theory.
Adrien-Marie Legendre (1752-1833)

Born in France.
He established the law of reciprocity of quadric residues and the law of the distribution of prime numbers.
He provided proof of the irrationability of pi and pi-squared.
He published a textbook and tables on elliptical functions.
Gottfried Wilhelm Leibniz (1646-1716)

Born in Germany.
He determined that the sum of the reciprocals of the triangular numbers equals 2.
He discovered the fundamental principles of calculus.
Marius Sophus Lie (1842-1899)

Born in Norway.
He discovered the transformation by which a sphere can be made to correspond to a straight line.
He also discovered that theoroms on aggregates of lines can be translated into theoroms on aggregates of spheres.
He developed the general theory of finite continuous groups of substitutions.
Nikolai Ivanovich Lobachevsky (1792-1856)

Born in Russia.
He founded non-Euclidean geometry concurrently with, but independently of, Karl Gauss and János Bolyai.
He showed that two geometric figures cannot have the same shape but different sizes.