I am writing the following sentence and would like to know which option is proper English (or if both are proper):
Option 1: Squaring both sides of (9) and dividing by 2 yields: [math equation]
Option 2: Squaring both sides of (9) and dividing by 2 yield: [math equation]
So the issue is "yield" versus "yields." Option 1 sounds better to me as a native English speaker. The sentence was actually written by my non-native co-author in the option 2 form. This made me wonder which is correct. Option 2 might be validated because both things together can be viewed as plural. Option 1 might be validated because the procedure of both things together is singular. Or perhaps both options are fine?
[Note that the "(9)" in the sentence refers to a numbered equation given earlier in the paper.]