**(March 31, 1596 – February 11, 1650)**

Famous for the Cartesian coordinate system which was named in his honor, René Descartes was one of 17th century’s most influential intellectuals. His interests included philosophy, mathematics, science, religion and general rationalism. As a key player in the scientific revolution which emanated from the Italian Renaissance, Descartes worked in France, Netherlands and Sweden. He made lasting and decisive contributions to Coordinate Geometry. His analyses (alongside those of Pierre de Fermat and others), laid the foundation for Leibniz’s and Newton’s discovery of Calculus. He was extremely inventive: solving problems and devising theorems such as the Rule of Sign for Polynomial Roots. Apart from developing and using this Rule of Sign to ascertain the number of positive and negative roots of a polynomial, Descartes is considered the first European to fully understand algebra’s power as an abstracting tool. He is also believed to be the first person who designate x, y and z as the unknowns in equations, while denoting the knowns with a, b and c. As a consummate free thinker, he sought ways of applying philosophy to everything he studied. Some of his treatises indicate that he delved deeply into: medicine, metaphysics and theology. His profound acumens ensured that he became a pathfinder in optics, mechanics and astronomy: as evident by the roles which his works played in the advancement of science. Descartes was very influential in his lifetime and has remained so centuries afterwards. In addition to several *Cartesian* concepts, the asteroid *3587 Descartes* is named after him.

The brain behind the Cartesian convention needs no introduction. It is immortal. Great summary though.

Hoje, eu fui para o frente praia com meu crianças. Eu encontrei uma concha do mar e deu para minha filha de 4 anos filha e disse “você ode ouvir o oceano se você colocar isso no seu ouvido.” Ela Coloque o shell para la ouvido e gritou. Havia um caranguejo eremita dentro e ele beliscou a orelha dela. Ela nunca quer voltar! LoL eu sei que é totalmente off-topic, mas eu precisava contar a alguém!

Wonderful like the rest! I’m enjoying your summaries.