M.B. Schiekel schrieb:
I'm using eqnarray with fleqn. Fine. Now I would like to reduce the vertical space before and after the eqnarray. So I read in the LaTeX Companion, I should change \topsep.
Don't do this, it will change the space between items in all lists of your document.
Instead of that, you can assure that the formula is not in a separate paragraph. This decreases the space around formulas and the surrounding text. But you can also put the formula in a separate paragraph (press ENTER before and after the equation) and use the dialog Layout->Paragraph to insert negative custom space before/after the equation.
You should only play with this space when your document is ready.
LaTeX normally uses the correct space, only if there is too much space left on a page, it will enlarge the space to fill out the whole page. In this case a forced pagebreak will help.
You find more (german) informations about multiline formulas in section 18 of the file "LyXMathebefehle":
http://wiki.lyx.org/LyX/LyXMathebefehle
regards Uwe
