In celebration of the Euler’s birthday, Google has created a doodle today. The doodle includes:

- The formula for the Euler characteristic, , which relates the number of vertices, edges and faces of a spherical polyhedron and it shows some of these polyhedra.
- It would not be a celebration of Euler without the identity that bears his name: , it is probably one of my most favourite identities! The doodle includes a geometrical interpretation of the formula too.
- The second “o” in the doodle is a 3D representation of a sphere and it is animated!! This makes reference to Euler angles to describe the orientation of a rigid body.
- Finally, they also make reference to the ‘Seven bridges of Königsberg‘ problem. With this problem, Euler effectively pioneered the area of mathematics known as graph theory.

Enjoy, and happy birthday Euler!