# Align* command is not working for my equation

I am using overleaf and I am using already "\usepackage{amsmath}".

But, with "align*" it dose not working and I don't have idea how I can fix it.

\begin{align*}
\begin{cases}
& ^{e}\mathrm{\hat{P}} = \, ^{e}\mathrm{V} \\
& ^{e}\mathrm{\hat{V}} = ge_{3}-\frac{f}{m}Re_{3}  \\
& \dot{\Theta} =  W \cdot \,^{b}\mathrm{\omega} \\
& J \cdot \,^{b}\mathrm{\dot{\omega}} \, = -^{b}\mathrm{\omega} \times (J \cdot \, ^{b}\mathrm{\omega})+G_{a}+\tau
\end{cases}
\end{align*}

• Welcome! What are you doing with all these \mathrms? How should e.g. \mathrm{\omega} be typeset?
– user194703
Jun 12 '20 at 3:40
• Thanks for your time ! I thought it is necessary when use left superscript. because it was used in page that I have referenced to learn how to use left superscript. ( I just did copy paste ;) ) after delete also situation is same..
– 유민재
Jun 12 '20 at 3:49
• \begin{align*} \begin{cases} ^{e}\mathrm{\hat{P}} & = \, ^{e}\mathrm{V} \\ ^{e}\mathrm{\hat{V}} & = ge_{3}-\frac{f}{m}Re_{3} \\ \dot{\Theta} & = W \cdot \,^{b}\mathrm{\omega} \\ J \cdot \,^{b}\mathrm{\dot{\omega}} \, & = -^{b}\mathrm{\omega} \times (J \cdot \, ^{b}\mathrm{\omega})+G_{a}+\tau \end{cases} \end{align*}
– 유민재
Jun 12 '20 at 3:56
• I solved it. ampersand should be placed left side of equal symbol.
– 유민재
Jun 12 '20 at 3:57

Are you looking for something like this? \prescript for the left superscript and aligned.

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\begin{align*}
\left\{\begin{aligned}
\prescript{e}{}{\hat{P}} &= \prescript{e}{}{V} \\
\prescript{e}{}{\hat{V}} &= g\,e_{3}-\frac{f}{m}R\,e_{3}  \\
\dot{\Theta} &=  W \cdot\prescript{b}{}{\omega} \\
J \cdot \prescript{b}{}{\dot{\omega}} &=
-\prescript{b}{}{\omega} \times (J \cdot
\prescript{b}{}{\omega})+G_{a}+\tau
\end{aligned}\right.
\end{align*}
\end{document}


align* is not needed here, you could use $...$, but since the question is on align*, I kept it.

• I appreciate for your help !
– 유민재
Jun 12 '20 at 6:58
• @유민재 I am always excited to meet other cats. ;-)
– user194703
Jun 12 '20 at 7:17

With use of \prescript defined in mathtools package (as suggested in @Schrödinger's cat answer ) and empheq math environment defined in the empheq package which also load mathtools:

\documentclass{article}
\usepackage{empheq}

\begin{document}
\begin{empheq}[left=\empheqlbrace]{align*}
\prescript{e}{}{\widehat{P}}  & = \prescript{e}{}{V}              \\
\prescript{e}{}{\widehat{V}}  & = g\,e_{3}-\frac{f}{m}R\,e_{3}    \\
\dot{\Theta}    & = W \cdot\prescript{b}{}{\omega}  \\
J \cdot \prescript{b}{}{\dot{\omega}}
& = -\prescript{b}{}{\omega} \times (J \cdot
\prescript{b}{}{\omega}) + G_{a}+\tau
\end{empheq}
\end{document}


• I appreciate for your help !
– 유민재
Jun 12 '20 at 6:58
• @유민재, you can up-vote the answer (by clicking on the up-pen at left top side of answer) and also accept one of received answer which you the most liked by clicking on the check mark at left top side of answer). Jun 14 '20 at 8:17