How to use alignat format

Question

I have this code:

\begin{alignat*}
    && u=\tan^{-1}{x} &&v=x\\
    && du=\frac{1}{1+x^2} &&dv=1
\end{alignat*}

And I am trying to align the u with du and v with dv. I get errors and the overleaf produces this: What am I doing wrong?

Edit: I have the following errors: Line 21: missing number, treated as zero Line 23: amsmath error: extra & on this line Line 23: Misplaced \omit

score 6 · Answer 1 · edited Dec 28 '21 at 10:29

6

Welcome to TeX.SE!

please always provide MWE (Minimal Working Example), a small but complete document, which we can compile as it is and which reproduce your problem
environment alignat requires data on how many columns you like to have (since you did not define them, you receive errors)

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{alignat}{3}
     u & = \tan^{-1}{x}     &\qquad &  v & = x\
    du & = \frac{1}{1+x^2}  &       & dv & = 1
\end{alignat}
\end{document}

If you like to have a bigger distance between columns with math expression, rather use align than alignat environment:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
     u & = \tan^{-1}{x}      &  v & = x\
    du & = \frac{1}{1+x^2}   & dv & = 1
\end{align}
\end{document}

edited Dec 28 '21 at 10:29

CarLaTeX

62,716

answered Dec 28 '21 at 10:16

Zarko

296,517

What does \qquad do? – Kai ML Dec 28 '21 at 10:22
1

@KaiML, it is simple to see :-). Remove it in observe difference in compiled result! It define distance between the first and last column. – Zarko Dec 28 '21 at 10:24
Ok, thank you very much! – Kai ML Dec 28 '21 at 10:26
@CarLaTeX, thank you very much for editing my answer! – Zarko Dec 28 '21 at 10:37
@Zarko You're welcome! – CarLaTeX Dec 28 '21 at 10:43

score 5 · Accepted Answer · answered Dec 28 '21 at 10:21

You must tell alignat how many “right-left” pairs of columns you want. And you have to provide the desired separation.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{alignat}{2}
& u=\arctan{x}       &\qquad& v=x\
& du=\frac{1}{1+x^2} &&       dv=1
\end{alignat}
\end{document}

I used “arctan” because I believe the symbol you use is mathematically wrong, so I cannot use it.

If you want to align at the = signs:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{alignat}{2}
 u&=\arctan{x}      &\qquad  v&=x\
du&=\frac{1}{1+x^2} &       dv&=1
\end{alignat}
\end{document}

@Kai This should be the accepted answer – Black Mild Dec 28 '21 at 10:35 — Black Mild, Dec 28 '21 at 10:35

How to use alignat format

2 Answers2