Abstract
This paper presents the first edition, translation and analyse of al-Mns commentary of the Book X of Euclid one. For the first time, irrational numbers are defined and classified. The algebraisation of Elementsrizms Algebra, shows irrational numbers as solution to algebraic quadratic equations. The algebraic calculus makes here the first steps. On this occasion, negative numbers and their calculation rules appears. Simplifications imposed by the algebraic writings are sometimes in opposition with the conclusions of propositions conceived in a purely geometrical framework, revealing a contradiction between geometrical and algebraic goals. It will be resolved by the independant way algebra will take with mathematicians belonging to the tradition of al-Karajal from the 11th-12th centuries on