In complex variable function, e (ix) = (cos x+isinx) is called Euler formula, e is the base of natural logarithm, and I is imaginary unit.

In topology, on any regular spherical graph, if R is used to record the number of regions, V is used to record the number of vertices, and E is used to record the number of boundaries, then R+ V- E= 2, which is euler theorem? It was first proved by Descartes in 1640, and later independently proved by Euler in 1752. We call it euler theorem, and some people abroad call it? Descartes theorem

A formula connecting complex exponential function and trigonometric function, where e is the base of natural logarithm and I is imaginary unit. It extends the definition of exponential function to complex number and establishes the relationship between trigonometric function and exponential function. It not only appears in mathematical analysis, but also occupies a very important position in the theory of complex variable functions, and is also called "overpass in mathematics".

This identity, also known as Euler formula, is the most fascinating formula in mathematics, which connects several most important numbers in mathematics: two transcendental numbers: the base e, pi of natural logarithm; Two units: imaginary unit I and natural unit1; And 0 is called one of the great discoveries of mankind. Mathematicians evaluate it as a "formula created by God".