Is there a way to achieve in LyX what one can achieve using \everymath{\displaystyle} in LaTeX, that is to force all inline math to look the same as math in equations (large integral signs, full-size numerator and denominator in fractions etc).
I have tried to add \everymath{\displaystyle} to preamble but it doesn't seem to help.
Update: Thank you, Torbjørn. I should have said that I actually want the change in LyX' WYSIWYG mode itself (if that's possible).
I don't see anyone say it explicitly but it appears you know that you can add it to your LaTeX preamble in LyX. This won't change how the equations display in LyX while you're editing them i.e. when your cursor is in them. However, if you also turn on instant preview (in preferences under graphics) then it will change how they look the rest of the time.
If you insert inline equations using the CTRL + M shortcut, you can redefine it to insert a displaystyle inline equation. Go to Tools > Preferences > Edition > Keyboard shortcuts. Search for the math-mode shortcut and edit the function to look like this: math-mode \displaystyle. You can assign a new shortcut if you want.
If you need to change the style of all the already inserted inline equations, I would do a regex search/replace in the .lyx file using, for example, Notepad++.
