Splitting equations using \begin{split} generates errors (again)

Question

I have been successfully using "split" to split up long equation, but now I get a new error:

 \begin{equation}
   \begin{split}
    \alpha_0=\frac{1}{\pi}\int_{-\pi}^{\pi}F(y)\text{d}y=\frac{2}{\pi}\int_{-\pi}^{-\frac{\pi}{2}}\text{d}y+\frac{1}{\pi}\int_{-\frac{\pi}{2}}^{0}\text{d}y+\frac{2}{\pi}\int_{0}^{\frac{\pi}{2}}\text{d}y+\frac{3}{\pi}\int_{\frac{\pi}{2}}^{\pi}\text{d}t\\ \alpha_0=\frac{5}{2}+\frac{3(\pi-\frac{\pi}{2}){\pi}
     \end{split}
\end{equation}

gives a lot of errors

I have tried many version, but can't get that $\alpha_0=\frac{5}{2}+\frac{3(\pi-\frac{\pi}{2}){\pi}$ to start at the second line, to the left...

Any ideas welcomed!

Thanks

I can't find the \begin{split} in your example... (and to split you use \\\, & is for align) — Rmano, Apr 24 '23 at 13:28
You have a runaway argument. Check it (writing the formula on different input lines, with logical spacing and indeneting, will help a lot). — Rmano, Apr 24 '23 at 13:32
\frac{3(\pi-\frac{\pi}{2}){\pi} is missing a closing brace for the outer fraction's numerator — Dai Bowen, Apr 24 '23 at 13:33
Unrelated, don't use \text like that. That is not what \text is for and in certain cases it will produce the wrong result. Use \mathrm{d} etc insted. — daleif, Apr 24 '23 at 13:34
Once you add the missing } and add a & in front of both the = signs, your code compiles just fine. — Jasper Habicht, Apr 24 '23 at 13:48

score 4 · Accepted Answer · edited Apr 24 '23 at 19:34

\frac{3(\pi-\frac{\pi}{2}){\pi} is giving an unmatched brace (this is presumably the first error you are seeing, and once resolved should fix the subsequent errors) and should probably be \frac{3(\pi-\frac{\pi}{2})}{\pi}.

Preferring \mathrm{d} (Is there a preference of when to use \text and \mathrm?), then you simply need to set an alignment point on the first equals sign

\documentclass{article}
\usepackage{amsmath}
\begin{document}
 \begin{equation}
  \begin{split}
   \alpha_0 &= \frac{1}{\pi}\int_{-\pi}^{\pi}F(y)\mathrm{d}y=\frac{2}{\pi}\int_{-\pi}^{-\frac{\pi}{2}}\mathrm{d}y+\frac{1}{\pi}\int_{-\frac{\pi}{2}}^{0}\mathrm{d}y+\frac{2}{\pi}\int_{0}^{\frac{\pi}{2}}\mathrm{d}y+\frac{3}{\pi}\int_{\frac{\pi}{2}}^{\pi}\mathrm{d}t\\ 
   \alpha_0 &= \frac{5}{2}+\frac{3(\pi-\frac{\pi}{2})}{\pi}
  \end{split}
 \end{equation}
\end{document}

score 3 · Answer 2 · answered Apr 24 '23 at 19:38

Compiling using aligned enviroment you get the same result.

\documentclass[12pt]{article}
\usepackage{amsmath}
\begin{document}
 \begin{equation}
  \begin{aligned}
   \alpha_0 &= \frac{1}{\pi}\int_{-\pi}^{\pi}F(y)dy=\frac{2}{\pi}\int_{-\pi}^{-\frac{\pi}{2}}dy+\frac{1}{\pi}\int_{-\frac{\pi}{2}}^{0}dy+\frac{2}{\pi}\int_{0}^{\frac{\pi}{2}}dy+\frac{3}{\pi}\int_{\frac{\pi}{2}}^{\pi}dt\\ 
   \alpha_0 &= \frac{5}{2}+\frac{3(\pi-\frac{\pi}{2})}{\pi}
  \end{aligned}
 \end{equation}
\end{document}

Splitting equations using \begin{split} generates errors (again)

2 Answers2