# [Tex/LaTex] Writing Equation in latex

amsmathequationssplit

I am new to Latex. I am trying to write this equation in Latex, but I've been getting the following error: Missing \$

\begin{equation} \label{tranfdc}
\begin{split}
T_v(s) &= \frac{V_{dc}(s)}{V_{dcref}(s)} &= \frac{\omega _B}{B}
\frac{k_{pdc}s + k_{idc}} {s^2 + \frac{ k_{pdc} \omega _B s} {B} +
\frac{k_{idc} \omega _B} {B}} \\

T_i(s) &= \frac{V_{dc}(s)}{i_{l}(s)} &= - \frac{\omega _B}{B} \frac{s} {s^2
+ \frac{ k_{pdc} \omega _B s} {B} + \frac{k_{idc} \omega _B} {B}}

\end{split}
\end{equation} • empty lines are forbidden in math environments
• environment split allow only one ampersand per equation line

\documentclass[11pt]{book}
\usepackage{amsmath}

\begin{document}
\begin{equation} \label{tranfdc}
\begin{split}
T_v(s) & = \frac{V_{dc}(s)}{V_{dcref}(s)}
= \frac{\omega _B}{B}
\frac{k_{pdc}s + k_{idc}} {s^2 + \frac{ k_{pdc} \omega _B s} {B} +
\frac{k_{idc} \omega _B} {B}} \\
%
T_i(s) & = \frac{V_{dc}(s)}{i_{l}(s)}
= - \frac{\omega _B}{B} \frac{s} {s^2
+ \frac{ k_{pdc} \omega _B s} {B} + \frac{k_{idc} \omega _B} {B}}
\end{split}
\end{equation}
\end{document}