User:Travailen/Set theory

Set theory

 * A discipline that applies iteration and recurrence (infinite procedure) to a subject (class).
 * Using iteration to build a function had been demonstrated by Hermann Hankel by his "principle of condensation of singularities'.
 * A sequence that converges to a point involves with infinite procedure too.
 * The intuition is zooming (bounded and converged) or gap (bounded but not converged). The term "closed" is used instead of "converged".
 * A set is closed if it contains all its limit points, it means the set converges to its limit points, while the boundary points of a divergent sequence are also called limit points. Thus "limit point" is an umbrella term, accumulation point (for convergence) is a kind of limit point.
 * Boundary points are the limit points of a closure at the boundary.