How can I convince my dad to let me see "Hangover part: II"?

okay so my dad wont let me see the hangover part II. I'm 14 and I've seen the first Hangover movie, I have also seen crude and scary movies that are rated R. My mom says that if my dad agrees, she'll take me. and im not really good at persuasion, so is there any advice that would help me convince him?