           2
yf := -----------
       a + b + 1
latex:\black$\displaystyle \begin{equation}$
latex:\black$\displaystyle  \mathrm{yf~:=~}\frac{2}{a+b+1}$
latex:\black$\displaystyle \end{equation}$
latex:\black$\displaystyle  \frac{2}{a+b+1}$
latex:\black$\displaystyle  \mathrm{\$}\frac{2}{a+b+1}\mathrm{\$}$
