I hardly say those forms but 아니다. I'd say 없다 instead of 있지 않다. 않다 is a negative and basic form of action verbs/quality verbs, 않는다 is the present one. I don't think there're any people say 있지 않다 as long as they ask people something(e.g. 걱정하지 마세요. 제가 여기 있지 않습니까? Don't worry. Ain't I here?(I'm here)) Although 않는다 is hardly used in spoken Korean, you can use it when you write a dairy or when you write a monologue like '이젠 그를 사랑하지 않는다 I don't love him any longer'. If you want to make negative verbs with this form, just remove '다' of the verb and add '-지 않는다' to the end of the rest. 공부하다 ⇒ 공부하 ⇒ 공부하지 않는다 Use '안 + a verb' when you talk with Korean people. Oh, and 공부하다(it's a kind of verb combined a noun with the verb, 'do') is originally 공부를 하다. So you should say 공부 안 한다. (공부 study, 안 not, 하다 do, (I) don't study.)