How do I change font in array environment inside an equation?

Question

I have the following code to define a piece-wise equation as shown in the following figure:

\begin{equation}
\label{xput_vc}
Throughput_{VC} = 
\begin{array}{cc}
  1 & N_{VC} \leq N_{slave} \\
  \frac{N_{req2slave}\times N_{VC}}{N_{req2slave}+Latency} &  N_{VC} > N_{slave} \\
\end{array}
\end{equation}

I want to decrease the font size of the conditions in that equation (NVC less then NSlave) but I can't seem to be able to get it to do that. I tried typing \footnotesize before the condition but it makes no difference.

How can I change the font size inside the array nested in an equation environment?

Answer 1

Here are ways to do it, with the cases environment. In the second way, you can have the 1 centred easily with \hfill (thanks to @Mico's suggestion):

    \documentclass{article}
    \usepackage{amsmath}

    \begin{document}

    \begin{equation}
      \label{xput_vc}
      \text{Throughput}_{VC} =
      \begin{cases}
        1 & \scriptstyle N_{VC} \leq N_\text{slave} \\
        \frac{N_\text{req2slave}\times N_{VC}}{N_\text{req2slave}+\text{Latency}} & \scriptstyle N_{VC} > N_\text{slave} \\
      \end{cases}
    \end{equation}
    \vskip1cm
    \begin{equation}
      \label{xput_vc}
      \text{Throughput}_{VC} =
      \begin{cases}
        \hfill 1\hfill & \scriptstyle N_{VC} \leq N_\text{slave} \\
        \frac{N_\text{req2slave}\times N_{VC}}{N_\text{req2slave}+\text{Latency}} & \scriptstyle N_{VC} > N_\text{slave} \\
      \end{cases}
    \end{equation}

    \end{document} 

Answer 2

You can do it like this

\text{\footnotesize $N_{VC} \leq N_{slave}$}