0\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 1\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 2\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 3\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 4\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 5\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 6\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 7\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 8\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*} 9\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}\begin{align*}\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}\end{align*}