### April 15 – Happy Birthday, Leonhard Euler

Posted on April 15, 2014

He's considered one of the greatest mathematicians of all times!

He's considered by most to be THE greatest mathematician of the 18th Century (the 1700s)!

In his own time, Euler was so famous among scientists and mathematicians that one of the greatest, Pierre-Simon Laplace, told students, “Read Euler, read Euler; he is the master of us all.”

Euler is also considered a physicist. Here are fields Euler made contributions to:
• infinitesimal calculus
• graph theory
• mathematical analysis
• mathematical terms notation
• mechanics
• fluid dynamics
• optics
• astronomy
• music theory

Born on this date in Switzerland, Euler showed his talent for math early. He entered a university at age 13, received his Master of Philosophy at age 16, and completed his doctoral dissertation at age 19. He was not able to get a job at his alma mater, in Switzerland, so he ended up moving to the Russian Empire to work as a physics professor. Eventually he moved to Berlin, in what was then Prussia but is now Germany, to continue as a professor of mathematics and physics.

Check out Eulerian Diagrams!

I have always called the sorts of illustrations seen here (above and right) Venn Diagrams, but John Venn himself called his diagrams Eulerian Circles. Euler had diagrammed subsets and disjoints with circles and other enclosed curves long before Venn was even born. However, Venn pointed out some problems with Euler's diagrams: apparently they are open to multiple interpretations rather than just one logical interpretation.

So Venn created a more restricted version of Eulerian diagrams, one in which all logically possible sets are represented. That means that, in a Venn Diagram, there will often be subsets that are empty. In the example below, which zone (or subset) of the Venn Diagram will be empty?
 (There are no animals that are both birds and mammals.)

Create your own Euler Diagram. Maybe you could make one that compares and contrasts insects and spiders, or that illustrates how various types of polygons, foods, or mammals are the same and different.

 Not all of Euler's diagrams were circles.Here are Euler Diagrams of triangles andquadrilaterals.

Also on this date:

New Year Celebrations in Cambodia and Laos