Scipione Dal Farro (1465-1526)
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- Born in Italy.
- He developed the solution to the depressed cubic equation, but another mathematician received credit for it.
- Jean Gaston Darboux (1842-1917)
- Born in France.
- He contributed to differential geometry and to the theory of surfaces.
- Julius Wilhelm Richard Dedekind (1831-1916)
- Born in Germany.
- He produced an arithmetic definition of continuity and an exact formulation of the concept of the irrational number.
- He devised axioms that formally and exactly represented the logical concept of whole numbers.
- He introduced the concept of dual groups.
- Abraham Demoivre (1667-1754)
- Born in France.
- Working with Johann Heinrich Lambert, the two created that part of trigonometry which deals with imaginary quantities.
- Gérard Desargues (1591-1661)
- Born in France.
- He developed a form of geometry, now known as projective geometry.
- René Descartes (1596-1650)
- Born in France.
- In his history of philosophy, Discours de la Méthode, he placed an appendix, titled La Géométrie, which was the first published account of what is known today as analytic geometry.
- Diocles (ca. 240 – ca. 180 BCE)
- Born in Greece.
- He solved the problem of doubling the cube, with which Greek mathematicians had struggled for centuries.
- He solved the problem of cutting a sphere with a plane so that the volumes of the two sections are in a particular ratio to each other.
- Diophantus (fl. 270-280 CE)
- Born in Alexandria.
- He devised the algebraic variable, in which a symbol stands for an unknown quantity.
- Equations needing only one symbol are now known as Diophantine equations.
- Lejeune Dirichlet (1805-1859)
- Born in Germany.
- He did research with the establishment of Fourier’s theorem.
- He researched the theory of numbers on asymptotiac laws.
