1. Position the cursor just inside the numerator (you should see 'Font: textrm' in the status line).
2. Hit backspace (removing the font selection and reverting the numerator to normal math font). 3. Select the contents of the numerator. 4. Type '\textsf' and hit the space bar. It will appear to be overwriting the numerator, but when you hit the space bar the numerator contents will be there, in the new font. 5. Repeat for the denominator. Paul