Jakob Bernoulli
Leonhard Euler
Leonhard Euler

Jakob Bernoulli

This stamp was issued in Switzerland at the occasion of the International Congress of Mathematicians that was organized in Zürich in 1994. It shows a portrait of the mathematician Jakob Bernoulli together with a formula and a graphics related to the following proposition: The arithmetic mean of a series of measurements of a value (under identical circumstances) tends to the expected value if their number increases (Law of large numbers, cf. also stamp of the month September 2004). Bernoulli's name
and the relevance of the formula are not mentioned on the stamp.

Leonhard Euler

This stamp was issued in Switzerland at the occasion of the 250th anniversary of the date of birth of the mathematician Leonhard Euler (1707 - 1783).

Leonhard Euler

... and here is the stamp in memory of his 300th birthday.

The left part shows a polyhedron as a solid body and its framework of edges (the actually not visible edges are presented in blue) as well as Euler's formula for polyhedrons. This formula states that for three-dimensional bodies without holes and with a surface built by planes the following relation holds:
The number of vertices e minus the number of edges k plus the number of faces f equals 2.