I will just say what I would do.

First, evaluate how much would you benefit from writing anything else but formulas. If the benefit is small I would not bother and follow Buffy's advice.

If the benefit is very big, I'd make two cheat sheets. One that is strict, and contains only formulas that I'd keep just in case and one that is useful for you. Then I would send an email to the professor, with the attached cheat sheet saying something along the lines

Dear Professor X.

Since I was not absolutely sure what you meant by "Formelsammlung" I am attaching my cheat sheet in here. If there are any problems please let me know before the test.

Thanks in advance,

monamona

Or whatever you feel comfortable with. That way the professor is at least more responsible to whether or not your cheat sheet follows the lines. (and you have already prepared a back-up if the Professor has problems with your current version).

I will just say what I would do.

First, evaluate how much would you benefit from writing anything else but formulas. If the benefit is small I would not bother and follow Buffy's advice.

If the benefit is very big, I'd make two cheat sheets. One that is strict, and contains only formulas that I'd keep just in case and one that is useful for you. Then I would send an email to the professor, with the attached cheat sheet saying something along the lines

Dear Professor X.

Since I was not absolutely sure what you meant by "Formelsammlung" I am attaching my cheat sheet in here. If there are any problems please let me know before the test.

Thanks in advance,

monamona

Or whatever you feel comfortable with. That way the professor is at least more responsible to whether or not your cheat sheet follows the lines. (and you have already prepared a back-up if the Professor has problems with your current version).