Take the formula

- e
^{i θ}= cos θ +*i*sin θ.

If θ = π radians, cos θ = -1 and sin θ = 0 so the formula becomes

- e
^{i π}= -1

or

- e
^{i π}+ 1 = 0,

a formula relating five key numbers in mathematics.

Take the formula

- e
^{i θ}= cos θ +*i*sin θ.

If θ = π radians, cos θ = -1 and sin θ = 0 so the formula becomes

- e
^{i π}= -1

or

- e
^{i π}+ 1 = 0,

a formula relating five key numbers in mathematics.