title: How to insert a long equation in whole page of two column format?
body: <p>I have an equation like this:</p>
  
  <pre><code>\begin{flalign}&amp;I(pair_1,pair_2)=\nonumber\\
      &amp;\begin{cases} 
          0 &amp; if\:\begin{cases}
          \max\left(r\left(pair_1^{rx}\right),r\left(pair_2^{tx}\right)\right)\leq
          d(pair_1^{rx},pair_2^{tx})  \\ \&amp; \\
          \max\left(r\left(pair_1^{tx}\right),r\left(pair_2^{rx}\right)\right)\leq
          d(pair_1^{tx},pair_2^{rx}) \end{cases}\\ 1 &amp; otherwise
      \end{cases}\nonumber\\
  \end{flalign}
  </code></pre>
  
  <p>I Want to show this equation in whole of two column page. Indeed avoid to put equation in only one column.</p>