font size in math eqnarray environment

[Tom Goldring]

I'm using LyX 2.4.2.1 in MacOS with Beamer to create a set of slides. In 
one of the slides I have a set of equations in an eqnarray, but it's too 
wide so in the pdf it goes all the way to the right side of the page 
(i.e. there is no margin on that side). How can I reduce the font size 
of that specific portion of the text?