\(\newcommand{\D}{\text{d}} \newcommand{\I}{\text{i}} \newcommand{\E}{\text{e}} \newcommand{\Prob}{\mathbb{P}} \newcommand{\Expect}{\mathbb{E}} \newcommand{\Var}{\text{Var}} \newcommand{\PAvg}[1]{\left[#1\right]} \newcommand{\Avg}[1]{\left\langle#1\right\rangle} \newcommand{\AvgJ}[1]{\Avg{#1}_{\bm J}} \newcommand{\AvgDyn}[1]{\Avg{#1}_{\text{dyn.}}} \newcommand{\CAvg}[2]{\Avg{#1}_{\left|#2\right.}} \newcommand{\Devi}{\mathfrak{d}}\)

計算テクニック

和の積の計算のための添字テクニック

課題

説明を追加

\left(
    \sum_i a_i
  \right)
  \left(
    \sum_i b_i
  \right)
=
  \left(
    \sum_i a_i
  \right)
  \left(
    \sum_j b_j
  \right)
=
  \sum_i \sum_j a_i b_j

\left(
    \sum_i a_i
  \right)^2
=
  \sum_i \sum_j a_i a_j