기여하신 문서�?저작권은 �?기여자에�?있으�? �?기여자는 기여하신 부분의 저작권�?갖습니다. $$ is TeX primitive syntax, which, as others have commented is hard to redefine (in traditional TeX there is absolutely no command name which triggers entering or leaving Display screen math). For making multiplication visually just like a fraction, a nested array can https://www.quora.com/profile/Kling-Ludie/