# tagging credit after gathering accumulation of equations

need help I need to put these three equations in three lines covered by a big parenthesis on the right side with the tag (Tolman 1939)

$$KP=e^{-\lambda} \Big( \frac {\nu'}{r}+ \frac {1}{r^2}\Big)-\frac {1}{r^2}$$

$$KP= e^{-\lambda} \Big(\frac {\nu ''}{2}-\frac {\lambda ' \nu '}{4} + \frac {(\nu')^2}{4} + \frac {\nu' -\lambda'}{2r}\Big)$$

$$K \rho c^2= e^{-\lambda}\Big (\frac {\lambda '}{r}-\frac {1}{r^2}\Big) +\frac {1}{r^2}$$

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Comment aside: you should not use $$…$$, which is plain TeX and can result in wrong vertical spacing. Use $…$ instead. –  Bernard Aug 5 at 10:05

You can add a brace on just one side with a \left. on one side and an \right\} to add the brace on the right.

## Code:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\left. \begin{aligned} KP &= e^{-\lambda} \Big( \frac {\nu'}{r}+ \frac {1}{r^2}\Big)-\frac {1}{r^2} \\ KP &= e^{-\lambda} \Big(\frac {\nu ''}{2}-\frac {\lambda ' \nu '}{4} + \frac {(\nu')^2}{4} + \frac {\nu' -\lambda'}{2r}\Big) \\ K \rho c^2 &= e^{-\lambda}\Big (\frac {\lambda '}{r}-\frac {1}{r^2}\Big) +\frac {1}{r^2} \end{aligned} \right\} \tag{Tolman 1939}
\end{document}

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A variant with a slighly simpler code, thanks to the empheq package (that loads mathtools, from the same author, and amsmath):

\documentclass{article}

\begin{document}

\begin{align*}[right = \empheqrbrace]
KP &= e^{-\lambda} \Big( \frac {\nu'}{r}+ \frac {1}{r^2}\Big)-\frac {1}{r^2}  \\
KP &= e^{-\lambda} \Big(\frac {\nu ''}{2}-\frac {\lambda ' \nu '}{4} + \frac {(\nu')^2}{4} + \frac {\nu' -\lambda'}{2r}\Big)  \tag{Tolman 1939}\\
K \rho c^2 &= e^{-\lambda}\Big (\frac {\lambda '}{r}-\frac {1}{r^2}\Big) +\frac {1}{r^2}
%
\end{align*}
\end{document}


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