History of Geometry
 

 

 

Contents

 

Early Geometry

 

Greek Mathematics

 

Euclid & the Elements

 

Later Developments

 

Analytic Geometry

 

Geometry Main Page 

Analytic Geometry
marriage of algebra & geometry
 
 
Analytic geometry was introduced in the 1630s. It was an important mathematical development, for it laid the foundations for modern mathematics as well as aided the development of calculus. The brainchild of Pierre de Fermat and Rene Descartes. The cartesian plane, the integral part of analytic geometry, is named after Descartes.
 
 
Pierre de Fermat (1601-1665)
 
Fermat was well-versed with Francois Viete's ideas for symbolization in algebra, and also tried to reconstruct Apollonius' theorems. His replacement of Apollonius' geometric analysis with algebraic ones led him to analytic geometry. He considered the relation between geometric loci and algebraic equations in two or more variables, as well as the framework for this, a system of axes where lengths can be measured against.
 
In his work, he came up with the idea of origin. He also used horizontal and vertical co-ordinates. Although he developed the basic ideas of modern analytic geometry, there are differences. The most notable are that he used only one axis, and only accepted positive solutions as "proper". He constructed a parabola, but did not consider the negative portion of it.
 
 
Rene Descartes (1596-1650)
 
Descartes made a greater impact with his analytic geometry because he published his work, which Fermat never did. His mathematical inclinations were discovered in a dream which he had whilst serving, under harsh conditions, in the Bavarian army. Some researchers believe he thought of the principles of analytic geometry in this dream.
 
Descartes' most significant writing is the Discours de la Methode pour bien conduire sa Raison et cher la Verite dans les Science (Discourse on the Method of Rightly Conducting the Reason in the Search for Truth in the Sciences). Analytic geometry appears in his section of La Geometrie. It is believed that he formulated the idea whilst watching a fly crawl along the ceiling of his room near a corner--he began expressing the path of the fly in terms of distance from the walls.
 
The algebraic notation that we use today was introduced by Descartes, where unknown quantities were represented by the last few letters of the alphabet and the constants by the first few. He also broke away from traditional trains of thought; instead of interpreting exponents in their geometrical sense such as areas or volumes, he regarded them as lines.
 
With the introduction of two axes of co-ordinates (however, he never formally introduced the second, or y, axis) and the idea of an origin, the co-ordinate system was born (Descartes never used the word co-ordinate, it was coined by Leibniz). He believed that curves are more complex than lines. He also said that geometric curves can be represented by an algebraic equation in two variables defining all their points. This is the fundamental idea of analytic geometry.
 

more on Fermat's and Descartes' works can be found in our section on history of calculus.