Csdrhrt

I am writing in IEEE double column environment. I have some equations with cases. For example, this equation seems to have too much space after the brace and also before and after the commas.

I was using the array environment which seems to cause those large spacing. I still prefer to have some independent control over the alignment of the three parts of the equation, since in some cases for each column, the length may be quite different, and I may choose to center, left, or right align for each column. What would be a good way to make those spacings smaller but still have control over the alignment?

The code I used for the equation is

begin{equation}

theta_{pk}=left{ begin{array}{ccc}

omega t+alpha+beta & , & n=1,2,3,4,5,6,ldots\

-omega t-alpha-beta & , & n=7,8,9,10,11,12,ldots

end{array}right.

end{equation}

as mentioned @marmot in comment, cases from amsmath is right tool for your job. it care for right spacing between building block of your equation:

documentclass{IEEEtran}

usepackage{amsmath}



usepackage{lipsum}  % for dummy text



begin{document}

lipsum[1]

begin{equation}

theta_{pk} =

    begin{cases}

omega t+alpha+beta   & , n=1,2,3,4,5,6,ldots\

-omega t-alpha-beta  & , n=7,8,9,10,11,12,ldots

    end{cases}

end{equation}

lipsum[2-4]

end{document}

addendum:
as mentioned @manooooh in his valued comment, AMS (American Mathematical Society) prefer style, where comas follows math expression, i.e:

     begin{cases}

omega t+alpha+beta,   & n=1,2,3,4,5,6,cdots,\

-omega t-alpha-beta,  & n=7,8,9,10,11,12,cdots.

    end{cases}

which use gives

but some people prefer the following style:

    begin{cases}

phantom{-}

 omega t+alpha+beta,  & n=1,2,3,4,5,6,cdots\

-omega t-alpha-beta,  & n=7,8,9,10,11,12,cdots

    end{cases}

giving:

however, documentation "amsldoc", as mentioned barbara beeton in her comment, is given the following example, how mathematicians usually use the cases math environment:

    begin{cases}

 omega t+alpha+beta  & n=1,2,3,4,5,6,cdots,\

-omega t-alpha-beta  & n=7,8,9,10,11,12,cdots.

    end{cases}

which gives:

A variant, with the fleqn environment from nccmath. I improvedged the alignment in the first column of the cases environment, using a phantom — sign in the first row.

You also can save some space – to a certain extent, with the mathrlap command from mathtools (which loads amsmath). I didn't need it here.

documentclass{IEEEtran}

usepackage{amsmath, nccmath}



usepackage{lipsum} % for dummy text



begin{document}



lipsum[1]

begin{fleqn}

begin{equation}

theta_{pk} =

    begin{cases}

phantom{-}omega t+alpha+beta, & n=1,2,3,4,5,6,ldots\

-omega t-alpha-beta, & n=7,8,9,10,11,12,ldots

    end{cases}

end{equation}

end{fleqn}

lipsum[2-4]



end{document}