Exponential of One

Theorem
Let $\exp x$ be the exponential of $x$.

Then:
 * $\exp 1 = e$

where $e$ is Euler's number: $e = 2.718281828\ldots$

Proof
We have that the exponential function is the inverse of the natural logarithm function:
 * $\ln e = 1$

Hence the result.