Accused of cheating because math proof is similar to online solution
I'll assume here that you didn't cheat, nor go outside the bounds of what is acceptable in your course.
The path, hopefully successful, is just to insist that you didn't cheat and keep on insisting on it. Don't try to &quot;prove&quot; that you didn't cheat. That isn't your job and will probably lead nowhere, or even to some &quot;gotcha moment&quot;. If you didn't cheat, say that and keep saying it.
If your work process was that you solved the problem on your own using course materials and your notes, then say that.
No one can, of course, guarantee that this or anything will be successful. If offered a follow up, possibly an oral question, consider taking it.
But accusations need to be proved, not assumed.
Good luck. The world isn't necessarily fair.