title: How to show \epsilon in R Markdown
body: <p>I am using R Markdown 1.0.9016 in RStudio 1.0.35 Windows.</p>
  
  <p>I used to be able to render equations like</p>
  
  <p>$\epsilon$</p>
  
  <p>But now it just shows \epsilon instead of rendering the epsilon symbol.</p>
  
  <p>What went wrong and how can I fix it?</p>