% This file is public domain. % % Test math displays. % \ifx\undefined\eplain \input eplain \fi %\loggingall A simple one, done with plain, for comparison (it should come out centered). Because of the way that \TeX's modes work, you should never leave a blank line (i.e., cause a par command) before a display. When \TeX\ sees a \$ in vertical mode, it switches to horizontal mode; but then when the display starts, it goes back to vertical mode, thus causing an extraneous blank line before the display. (Plain \TeX\ sets abovedisplayskip to about a baselineskip, so you are going to get one blank line from that (unless the line above the display is short, in which case aboveshortdisplayskip is used, which is 3pt or some such); but if a par intervenes between the end of the paragraph and the beginning of the display, you get a second one.) $$x = y + z$$ After a centereddisplays: \centereddisplays $$d+e+f$$ Now starting leftdisplays. \leftdisplays No equation number: $$A = B + C$$ Do another leftdisplays. \leftdisplays $$a+n=m$$ Equation number on right: $$D = E + F\eqno (r)$$ Equation number on left: $$G = H + I\leqno (l)$$ Using eqdef: $$J = K + L\eqdef{hello}$$ Here is one done with displaylines: $$\displaylines{x=1\cr}$$ Let's do those again, indented by one inch plus the paragraph indentation: {\leftdisplayindent = 1in No equation number: $$A = B + C$$ Equation number on right: $$D = E + F\eqno (r)$$ Equation number on left: $$G = H + I\leqno (l)$$ Using eqdef: $$J = K + L\eqdef{hello}$$ Here is one done with displaylines: $$\displaylines{x=1\cr}$$ } \hrule \smallskip The rule above just makes it easier to see the margins. Another displaylines, this one should end up on the right. $$\displaylines{\hfill y=2\cr}$$ A displaylines with an eqno: $$\displaylines{x=1 \eqno{d}\cr}$$ A displaylines with an eqdef: $$\displaylines{x=1 \eqdef{eqdef-displ}\cr}$$ {\leftskip = 14pt An indented displaylines with an eqdef: $$\displaylines{x=1 \eqdef{eqdef-displ}\cr}$$ } Here is one with done with eqalign (the ='s should line up): $$\eqalign{ a+b&=c\cr dq+er&=f\cr }$$ An eqalign with a noalign inside: $$\eqalign{ a+b&=c\cr g+h&=i\cr }$$ And one with eqalignno: $$\eqalignno{ a+b&=c&(1)\cr d+e&=f&(1*)\cr g+h&=i&\eqdef{eqdef-2}\cr }$$ An eqalignno with a noalign inside: $$\eqalignno{ a+b&=c&(1)\cr \noalign{and} g+h&=i&\eqdef{eqdef-2}\cr }$$ And one (indented more) with leqalignno: {\leftdisplayindent = 1in $$\leqalignno{ a+b&=c&(1)\cr dt+eg&=f&(1*)\cr g+h&=i&\eqdef{eqdef-3}\cr }$$ } A cases, from p.175 of the TeXbook. $$ |x| = \cases{x, &if $x\ge0$;\cr -x, &otherwise.\cr }$$ A pmatrix, from p.176. $$\pmatrix{ x-\lambda&1&0\cr 0&x-\lambda&1\cr 0&0&x-\lambda\cr }$$ The rule below just makes it easier to see the margins. \smallskip \hrule \bigskip Back to centered displays now. \centereddisplays No equation number: $$A = B + C$$ Equation number on right: $$D = E + F\eqno (r)$$ Equation number on left: $$G = H + I\leqno (l)$$ Using eqdef: $$J = K + L\eqdef{hello}$$ Here is one done with displaylines: $$\displaylines{x=1\cr}$$ \hrule \smallskip The rule above just makes it easier to see the margins. Another displaylines, this one should end up on the right. $$\displaylines{\hfill y=2\cr}$$ Here is one with done with eqalign (the ='s should line up): $$\eqalign{ a+b&=c\cr dq+er&=f\cr }$$ And one with eqalignno: $$\eqalignno{ a+b&=c&(1)\cr d+e&=f&(1*)\cr g+h&=i&\eqdef{eqdef-2}\cr }$$ An eqalignno with a noalign inside: $$\eqalignno{ a+b&=c&(1)\cr \noalign{and} g+h&=i&\eqdef{eqdef-2}\cr }$$ And one (indented more) with leqalignno: {\leftdisplayindent = 1in $$\leqalignno{ a+b&=c&(1)\cr dt+eg&=f&(1*)\cr g+h&=i&\eqdef{eqdef-3}\cr }$$ } The rule below just makes it easier to see the margins. \smallskip \hrule \bigskip A cases, from p.175 of the TeXbook. $$ |x| = \cases{x, &if $x\ge0$;\cr -x, &otherwise.\cr }$$ A pmatrix, from p.176. $$\pmatrix{ x-\lambda&1&0\cr 0&x-\lambda&1\cr 0&0&x-\lambda\cr }$$ Now after a second centereddisplays: \centereddisplays $$a + b = c$$ \end