6

I was googling the way of adding 3 dots between two equations, I found this question> (Vertical alignment of dots in equation)

What I want:

  • Three equations.
  • Between equation 2 and 3 I want 3 dots.

When I implemented their way into my equation, I got a really funny equation:

\begin{alignat}{1}
x_{0} = y + m_{0} \\
x_{1} = y + m_{1} \\
\vdotswithin{x_{1} = y + m_{1}}
x_{n} = y + m_{n}
\end{alignat}

the result:

enter image description here

questions:

  1. how do i make these dots above the third equation and in the center?

  2. why do I have to write the equation twice, once with
    \vdotswithin{equation} and once without it? is there another way?

  3. how do I only get equation numbers for the actual equations without the dots? because when i implement it the dots are numbered as an equation.

Edit 1: Replaying to @Thomas's answer this:

\begin{align*}
   x_{0} &= y + m_{0} \\
   x_{1} &= y + m_{1} \\
   &\vdots\\
   x_{n} &= y + m_{n}
\end{align*}

produces this:

enter image description here

the dots are still not aligned to the equal sign or at least the middle of the equation. How can i modify that?

  • See the modified answer. – Thomas Apr 23 '16 at 11:53
  • 2
    You have to use &\vdotswithin{=}. – Manuel Apr 23 '16 at 12:12
11

I think you can simplify a bit and use something like this (from the amsmath package):

\begin{align}
   x_{0} &= y + m_{0} \\
   x_{1} &= y + m_{1} \\
   &\;\;\vdots \notag \\
   x_{n} &= y + m_{n}
\end{align}

The notag command removes the equation numbering from the line with the vertical dots. I am sure there is a way of adding the exact amount of white space (equal to half the width of the equals sign) to center the dots under the =, but this does the job in a rather simple manner.

EDIT (with inspiration from Manuel's comment)

The mathtools package provides two versions of the vdotswithin command (notice the missing \\ in the short version).

\begin{align}
   x_{0} &= y + m_{0} \\
   &\shortvdotswithin{=}
   x_{1} &= y + m_{1} \\
   &\vdotswithin{=} \notag \\
   x_{n} &= y + m_{n}
\end{align}

Resulting in:

enter image description here

6

You don't have to write the equation twice: you have to write the relation symbol w.r.t. which the dots will be centred. Illustration with \vdotswithin and \shortvdotswithin:

\documentclass{article}

\usepackage{mathtools}

\begin{document}

\begin{align}
  x_{0} & = y + m_{0} \\
  x_{1} & = y + m_{1} \\
        & \vdotswithin{ = }\notag \\
  x_{n} & = y + m_{n}
\end{align}

\begin{align}
  x_{0} & = y + m_{0} \\
  x_{1} & = y + m_{1} \\
        & \shortvdotswithin{ = }\notag \\[-3.5ex]
  x_{n} & = y + m_{n}
\end{align}

\end{document} 

enter image description here

  • I am sorry for the overlap, but I was editing my answer while you posted yours so I didn't notice. What is the reason for \\[-3.5ex] after the short version? – Thomas Apr 23 '16 at 12:27
  • 1
    It's to get the vdots vertically centred between eqs (5) and (6) – Bernard Apr 23 '16 at 12:31
  • @Thomas: It seems there's a detail I hadn't seen in the use of \shortvdotswithin… I've learnt something today :o) – Bernard Apr 23 '16 at 12:34
  • It looks like it. Although I think including the linebreak (without adjusting space afterwards) would add to the consistency of the notation. – Thomas Apr 23 '16 at 12:37
  • What I couldn't find is how to change the vertical spacing in \shortvdotswithin – a little too tight for my taste. It works with a system key=value, but when I write modifications in my preamble, the compiler complains… – Bernard Apr 23 '16 at 12:53

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