Easy 10 points to first lagit answer- teacher preferred?

ok i was taking the science midterm today and i was using a graphing calculator. As it seems i got it from my math teachers shelf bc she let me use it. As i got extra time i was doing a equation on how to find a calorie of an object. As i finished the answer i pressed aps and i didnt know how to get out so i clicked random ons. I then went onto a page with notes on it (about sciecne). after i started to write my answer (becuase i didnt know how to get out) he saw letters on my calculator. HE accused of me cheating and i wasnt so i showed him how to get there. And then i asked can you give me one more chance (because i DIDNT cheat) and hes like then how did you get there. I said i accidently pressed the apps on and i didnt know how to get out so i clicked randomly and i somehow got there. And he said i was lying. How do i persuade him to believe me?