# Laplace Transform of Power

## Theorem

### Laplace Transform of Positive Integer Power

Let $\laptrans f$ denote the Laplace transform of a function $f$.

Let $t^n: \R \to \R$ be $t$ to the $n$th power for some $n \in \N_{\ge 0}$.

Then:

$\laptrans {t^n} = \dfrac {n!} { s^{n + 1} }$

for $\map \Re s > 0$.

### Laplace Transform of Real Power

Let $n$ be a constant real number such that $n > -1$

Let $f: \R \to \R$ be the real function defined as:

$\map f t = t^n$

Then $f$ has a Laplace transform given by:

 $\ds \laptrans {\map f t}$ $=$ $\ds \int_0^\infty e^{-s t} t^n \rd t$ $\ds$ $=$ $\ds \frac {\map \Gamma {n + 1} } {s^{n + 1} }$

where $\Gamma$ denotes the gamma function.

### Laplace Transform of Complex Power

Let $q$ be a constant complex number with $\map \Re q > -1$.

Let $t^q$ be the the principal branch of the $q$-th complex power whose domain contains the half-plane $\map \Re s > 0$.

Then $t^q$ has a Laplace transform given by:

$\laptrans {t^q} = \dfrac {\map \Gamma {q + 1} } {s^{q + 1} }$

where $\Gamma$ denotes the gamma function.