Trigonometry/e to the i Pi

< Trigonometry

Take the formula

e^{xi}=\cos(x)+i\sin(x) .

If x=\pi radians, \cos(x)=-1 and \sin(x)=0 so the formula becomes

e^{\pi i}=-1

or

e^{\pi i}+1=0

a formula relating five key numbers in mathematics.