I am in a small electricity and magnetism class, and I have recently become aware of other students using an online solution sheet (on slader.com). On the most recent homework, I (who didn't use the online solution sheet) got a significantly worse grade than I expected. When I read the TAs posted solutions, I realized that he had made all of the same mistakes (the primary one being assuming that the parallel impedance formula is 1/(Z_1)+1/(Z_2) when it is actually 1/(1/(Z_1)+1/(Z_2))) and all of the exact same approximations as the online solution sheet. It is clear that he basically copied from the online solutions. What's worse, he marked many of my solutions wrong: both the ones where I had different (more accurate) approximations and the ones that were correct, but different from his incorrect solutions (the professor confirmed that my solutions are correct).
I'm guessing it isn't against the rules for a TA to use an online solution sheet, but the fact that he has been using the same one that many of the students are using means that this entire semester I have been at a significant disadvantage. I have done well, but the class is curved so there's that also.
What do I do about this?