Favorite math formula?

Question

What is your favorite math formula? Mine is

e^(i*pi)+1=0

Answer 1

Euler's formula is pretty cool. If you have a graph embedded on the plane, (If you don't know what this is, think of points on a piece of paper with lines connecting the points, where none of the lines can cross). Then Euler's formula says that:
V - E + F = 2.
Here V is the number of vertices(points), E is the number of edges(lines), and F is the number of faces (The spaces enclosed by the lines).

There are variants on this formula for any surface, on the projective plane it's V - E + F = 1. On the torus it's V - E + F = 0. On the Klein bottle it's V - E + F = -1, etc.

Answer 2

I teach 6th grade math--my favorite formula for kids that age is length X width = Area. It's easy to remember and everyone gets it right!!

Answer 3

Fatou's Lemma: Let (X, M. m) be a measure space. If f_n is a sequence of mesurable functions defined on X and with values in [0 ,
oo], then Integral liminf f_n dm <= liminf Integral f_n dm. This lemma has a key role in mesure theory.

I also like the mean value theorem: f(x) - f(y) = (x - y) f'(u).

Answer 4

why would i have a favorite? math s**ks.

i like the Pythagorean therm a2+b2=c2 because its easy to use to find the hypotenuse of a triangle and the only one i know! lol

Answer 5

i like the quadratic formula
i can't remmeber it though lol!

Answer 6

(a+b)-(a+b)+(a+b)
i love that formula

Answer 7

π = (1/√-1)Log(-1)

Answer 8

se^x=e^x