Aligning the Left Hand Side of a big equation with fraction

Question

After spending quite some time making sure this wasn't already answered, I decided to post this anyway, as I haven't found what I'm looking for.

I have this equation with nested fractions, and I want the Left Hand Side to be centered with respect to the Right Hand Side. It now appears at the hard left corner, I want it to be in the middle. See the picture below for an example.

\documentclass[]{Article}
\usepackage{amssymb,amsmath} 
\begin{document}

\begin{math}

\ C(m) =  \cfrac{D_1(K_1+mK_2)}{1- \cfrac{1}{ \left(  \cfrac{D_1+D_2}{D_2} \right) ^{m+1}- \cfrac{D_1}{D_2}}}
\end{math}

\end{document}

Answer 1

I would advise against this, since the display seems confusion. The fractional content is aligned, vertically, to the outer \frac's math axis, which is located at the horizontal rule. However, you can fake a fraction using an array, that has a vertically centered math axis regardless of the location of the horizontal rule:

\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}

\[
  C(m) = \cfrac{D_1(K_1 + mK_2)}
    {1 - \cfrac{1}
      { \left( \cfrac{D_1 + D_2}{D_2} \right)^{m+1} - \cfrac{D_1}{D_2}}}
\]

\[
  C(m) = \begin{array}{@{}c@{}}
    D_1(K_1 + mK_2) \\ \hline
    1- \dfrac{\strut 1}
      { \biggl( \dfrac{D_1 + D_2}{D_2} \biggr)^{m+1} - \dfrac{D_1}{D_2}}
    \end{array}
\]
\end{document}

There didn't seem to be a need for using the continued fractions.