How to make the equations at the center

Question

(I'm using LyX).

When I'm writing multiline equations, with \aligned the align of the equations is right, how can I make it to be center?

For example: Here how it looks when I writing at math mode:

And this is what happens what I get out from it:

How can I make that it will be centered?

Thank you!

Answer 1

One normal usecase of aligned is to align certain elements, typically the (in)equality signs, of the different lines while having a single equation number for the whole set. (As opposed to numbering each line separately.)

aligned is basically a tabular structure where the columns are aligned as rlrlrlrl.... That is, the first, third etc. columns are right aligned, the second, fourth etc. are left aligned. To align equations by the equals sign, put the left hand side of the equations in the first column of the aligned, the equals sign and the right hand side in the second column. (The = should not be in the first column, the spacing will be wrong.)

In LyX, when you do Insert --> Math --> Aligned environment, LyX adds two columns, indicated by the two blue boxes:

To write something left aligned, put it in the second of these two boxes. To add new columns you click the New column button -- -- on the Table toolbar (usually found on the bottom of the LyX window).

If you don't need any alignment, use gathered instead, which just centres the lines.

Note that both aligned and gathered are intended for use within other math environments, such as the normal \[ ... \] or the equation environment. Their counterparts align and gather are displayed math environments in their own right, and should not be used within other math constructs. align and gather will number each line, but have also got unnumbered versions, align* and gather*. The unnumbered versions are used by default in LyX when you do Insert --> Math --> AMS Align/Gather.