Here we start the series of posts for plane geometry. In it, we will talk from very primitive concepts, to more advanced concepts, aimed at children (elementary to medium). Start using geometry The Greeks of ancient civilization were one of the most famous people in the art of thinking. They were responsible for the heyday of philosophical, scientific, political, social and artistic ideals and had a decisive influence on the western world.
In this post we will study the primitive elements of mathematics, which are fundamental to the elements of mathematics. This chapter is dedicated to set theory, however, let’s take it slowly. In each post we will talk a little about this complex and dense theory. In set theory it is necessary to have some primitive notions: primitive notions of set. primitive notions of membership, which we use the symbol belongs $\in$. Relevance In relevance, the relationship between sets can be established as follows: