# Happy 306th birthday Euler!

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

• The formula for the Euler characteristic, $V-E+F=2$, 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: $exp[i pi]=-1$, 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!

Euler doodle