how to change the font of equations?

Hi, I need to change the style of equations from being italic to being straight, the best font should arial or something similar. Is there a command for that?

You can use either \mathrm{abc] for Roman upright font.

or perhaps more universal is \textup{abc}

thanks. however, it solved my problem just partly. I want to write something like \mathsf{E_0=\hbar\omega_0} because otherwise my formula is hard to read. However, \mathsf seems to change only the format of E_0 but has no effect (like other formats) on hbar or omega_0. textup only makes a repeated series of decreasing hbars, but they are still itallic.

thanks. however, it solved my problem just partly. I want to write something like

E_0=hbar*omega_0

(latex like) and in readable font, say like the one of this editor or similar to arial because otherwise my formula is hard to read. However, mathsf seems to change only the format of E_0 but has no effect (like other suggested formats) on hbar or omega_0. textup only makes a repeated series of decreasing hbars, but they are still itallic and hard to read.