ruhoh plugin to overload the redcarpet parser with mathjax tags

mathjax.rb

# place mathjax.rb in _plugins directory of your blog
require 'redcarpet'
class HTMLwithAlbino < Redcarpet::Render::HTML
  def block_code(code, language)
    if language == 'mathjax'
      "<script type=\"math/tex; mode=display\">
        #{code}
      </script>"
    else
      "<pre><code class=\"#{language}\">#{code}</code></pre>"
    end
  end
  
  def codespan(code)
    if code[0] == "$" && code[-1] == "$"
      code.gsub!(/^\$/,'')
      code.gsub!(/\$$/,'')
      "<script type=\"math/tex\">#{code}</script>"
    else
      "<code>#{code}</code>"
    end
  end
end

class Ruhoh
  module Converter
    module Markdown

      def self.extensions
        ['.md', '.markdown']
      end
      
      def self.convert(page)
        markdown = Redcarpet::Markdown.new(HTMLwithAlbino.new(:with_toc_data => true), 
        :autolink => true, 
        :fenced_code_blocks => true
        )
        markdown.render(page.content)
      end
    end
  end
end

sample

---
title: Numerical Differentiation
description: 

layout: page
---

## Derivative of a real function

The derivative of `$f(x)$` is

````mathjax
\begin{equation}
f'(x) = \lim_{h \rightarrow 0} \frac{f(x + h) - f(x)}{h} \label{eq:DerivativeDef}
\end{equation}
````
suggest a naive approach to compute a numerical derivative: pick a small value `$h$` and apply \eqref{eq:DerivativeDef}. However, applied uncritically, this procedure is almost guaranteed to produce inaccurate results.

[Ridders](#Ridders) applied Romberg's method to improve the accuracy in the computation of the first and second derivatives of a real function. Using the Taylor expansion in the vicinity of `$x$`:

$$
f'(x) \approx \frac{f(x + h) - f(x - h)}{2h}
$$

with a truncation error of `$e_t \sim h^2 f^{(3)}$`. As a consequence, `$e_t$` decreases quadratically with decreasing `$h$`.

Is it possible to use only $e^x$ (without backticks) to trigger MathJax?