# Large delimiters, multiline equations

Paul A. Rubin parubin73 at gmail.com
Fri Jan 22 19:09:23 UTC 2021

On 1/22/21 1:06 PM, Neal Becker wrote:
> On Fri, Jan 22, 2021 at 11:26 AM Joel Kulesza <jkulesza at gmail.com> wrote:
>> On Fri, Jan 22, 2021 at 6:29 AM Neal Becker <ndbecker2 at gmail.com> wrote:
>>> I have an equation that has to be split (to fit into beamer
>>> presentation).  It has large delimiters that span the lines.  Does lyx
>>> have any facility to help with this?  I did get a useable result, but
>>> only with a lot of ERT.  Lyx seems not helpful here, is there any way
>>> other than ERT to get "\Biggl. ... \Biggr]"?  Or "\right."?
>>>
>>> Here is what I wanted:
>>>
>>> \begin{multline*}
>>>
>>> \mathbf{X}_{N_{C}\times S\times
>>> A}=\left[\left[\left[\sum_{n}m1_{p+cL_{c}+nS}m2_{p+cL_{c}+(n+\tau)S}^{*}\right.\right.\right.,\\
>>>
>>> \Biggl.\Biggl.\Biggl.\tau\in[-A/2\dots A/2]\Biggr],p\in[0\dots
>>> S-1]\Biggr],c\in[0\dots N_{c}-1]\Biggr]
>>>
>>> \end{multline*}
>>
>> To accomplish this, I prefer to use the Insert Delimiters capability (the subject of an adjacent thread).  Using "none" will let you give the appearance of matched delimiters that vertically scale to contain the contents.  The "Swap & Reverse" button is meant as a convenience to control delimiter insertion in this manner.  Finally, if you have lines that vary in vertical extent, a vertical phantom (\vphantom) with the proper contents will ensure consistent delimiter sizes.
>>
>> Hope this helps,
>> Joel
> Thanks for the reply.  I can't see how to do this.  Inserting
> Delimiters seems to insist on inserting a pair of delimiters - I don't
> see any way to just get \left[ for example.
I've attached three screenshots. The first (shot1.png) shows LyX open
with a new document, containing two copies of your example. The first
copy is pasted into an ERT box (so that I can see what you are shooting
for). The second has most of your example, but not the nested brackets,
typed into a multiline math environment. The first line of the multiline
formula is selected, so that I can put a left bracket in front of it.

The second screenshot shows the delimiter insertion dialog. Note that I
unchecked the "keep matched" box below the left pane, then selected a
left bracket in the left pane and "(None)" in the right pane.

The third screenshot shows the formula after I click "Insert" in the
delimiter dialog. There is a large left bracket at the start of the
first line and "phantom" bracked (dotted line) at the end of the first
line. To insert other brackets, do similar things, selecting the content
of the bracketed area and where appropriate selecting none on the left
and a closing bracket on the right.

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