Confuse you seems to be too much confused so you proved theorem no 15 where the question was to prove theorem no 18. Don`t worry happens... had happened with me too. For me cheating is .. When I know that I am wrong and do it pretending as If I am right and get the wrong result (even right result) For me I don`t mind even my girl sleep with others that is not cheating for me...as long as she keeps quiet but cheating is when she says that she was remembering me all the time as they were penetrating ...