$\exp x = 1 + x + x^2/2 + x^3/6 + x^4/24 + \cdots$.

$\exp x = 1 + x + x^2/2 + x^3/6 + x^4/24 + \cdots$.

\begin{align*}
  &
  \Z\subset\Q\subset\R\subset\C
  \\ &
  \diag(a_1,\ldots,a_n) =
  \begin{bmatrix}
    a_1     & 0      & \cdots & 0 \\
     0      & a_2    & \ddots & \vdots \\
     \vdots & \ddots & \ddots & 0 \\
     0      & \cdots & 0      & a_n \\
  \end{bmatrix}
  \qquad (\text{diagonal matrix})
  \\ &
  a\mapsto\np{:}{a} \qquad \text{(the normal ordering of $a$)}
\end{align*}

Here \Z, \Q, \R, \C, \diag, and \np are defined in MyConfig.js.

\begin{align*} & \Z\subset\Q\subset\R\subset\C \\ & \diag(a_1,\ldots,a_n) = \begin{bmatrix} a_1 & 0 & \cdots & 0 \\ 0 & a_2 & \ddots & \vdots \\ \vdots & \ddots & \ddots & 0 \\ 0 & \cdots & 0 & a_n \\ \end{bmatrix} \qquad (\text{diagonal matrix}) \\ & a\mapsto\np{:}{a} \qquad \text{(the normal ordering of $a$)} \end{align*}