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Solve the following mathematical rebus, where the main point is to be able to understand what is being shown in each line.
$$
4\sum_{n=0}^{\infty}\frac{(-1)^n}{2n+1}\\
(-\infty,...,-1,0,1,...,\infty)\times(-\infty,...,-1,0,1,...,\infty)\\
\forall\begin{bmatrix}{-1}&{0}\\
{0}&{-1}
\end{bmatrix}
...