Rene Descartes

Rene Descartes was a French mathematician and philosopher who lived in the 1600s. He had a big idea: he connected algebra and geometry together. The coordinate grid you use in math class was his invention.

The Coordinate Plane

Descartes invented the coordinate plane, which has an x-axis and a y-axis. Any point can be described with two numbers, like (3, 5). This idea let people use algebra equations to draw shapes.

Before Descartes, algebra and geometry were separate subjects. He showed they were really two sides of the same coin. This was a huge breakthrough.

A Great Thinker

Descartes was also a famous philosopher. He is known for saying I think, therefore I am. He believed that thinking and questioning were the most important things a person could do.

He wrote books about math, science, and philosophy. His ideas about using logic and reason to understand the world changed how people think.

Fun Facts

• The coordinate plane is sometimes called the Cartesian plane, named after Descartes.
• Legend says Descartes got the idea for coordinate grids while watching a fly on his ceiling.
• Descartes also studied optics, the science of light, and helped explain how rainbows form.

Did You Know?

Descartes liked to sleep in very late. He often stayed in bed until noon, thinking about math and philosophy. Some of his best ideas came to him while lying in bed!