# Problem with using pause and onslide in one frame

I'm trying to use \pause in align mode but it's not working. I ended up using onslide which it works fine. However, when I use both of them in one frame, some of onslide work while the other are not. This is a minimal example to regenerate the problem.

\documentclass[t]{beamer}

\usepackage{amsmath}

\begin{document}

\begin{frame}
AAAAA CCCCCC \\
\pause
AAAAA CCCCCC
\begin{align*}
\onslide<1->{a &= b \\}
\onslide<2->{b &= c \\}
\onslide<3>{ a &= c}
\end{align*}
\end{frame}

\end{document}

As you can see, the first two lines show up together. While the third line appears in the next slide. When I comment out \pause, the problem goes away. How to overcome this issue?

The "problem" is, that the first pause already creates an overlay, so you have to start counting at 2 in the align and not at 1. But to make this more flexible, simply don't use hard coded numbers but relative overlays.

\documentclass[t]{beamer}

\usepackage{amsmath}

\begin{document}

\begin{frame}
AAAAA CCCCCC \\
\pause
AAAAA CCCCCC
\begin{align*}
\onslide<+->{a &= b \\}
\onslide<+->{b &= c \\}
\onslide<+>{ a &= c}
\end{align*}
\end{frame}

\end{document}
• With the above approach, onslide has no impact on number of equations if the mode is align. Any suggestions? – CroCo Oct 16 '16 at 10:34
• Yes, my suggestion would be not using align. Otherwise tex.stackexchange.com/a/323432/36296 might be of interest, the long explanation can be found at "23.4 Uncovering Tagged Formulas Piecewise" in the beamer user guide. – samcarter_is_at_topanswers.xyz Oct 16 '16 at 10:53
• "23.4 Uncovering Tagged Formulas Piecewise" solved my problem. Thank you. – CroCo Oct 16 '16 at 11:17

The \pause command does exactly what it says: stops the frame where it is. As such, if you then specify slide 1 later on in the frame, that material will appear with slide 2, as you've observed. I strongly advise not mixing \pause with any more complex overlay control: \pause is simple but limited, other overlay specs are more complicated but as a result more powerful. Sam Carter's answer shows that if you want the align to appear after the text, it's easy with a mix of approaches. If you want the two to appear at the same time, I'd go with something like

\documentclass[t]{beamer}

\usepackage{amsmath}

\begin{document}

\begin{frame}
\onslide<+->{AAAAA CCCCCC} \\
\onslide<+->{AAAAA CCCCCC}
\begin{align*}
\onslide<.(-1)->{a &= b \\}
\onslide<.->{b &= c \\}
\onslide<+->{ a &= c}
\end{align*}
\end{frame}

\end{document}

(See Relative overlay specification in beamer? for more on relative overlay specifications.)

• Why with align, number of equations show up before the equations? – CroCo Oct 16 '16 at 10:37
• @CroCo The align environment is set twice, and this makes life very tricky: this is mentioned in the beamer manual – Joseph Wright Oct 16 '16 at 10:39