Question

Aren't an and the are articles .Why they are adjectives here? why not and why yes?

Answer 1

First make your self clear that parts of speech is different from articles.To make you more clear let me say an example.
there are many kinds of pen like ball pen,ink pen and other types are Black pen,blue pen and much more.
So here the words an and the has two kinds of forms namely as articles and even as adjective (when formed into sentences).