Resumen de Determinación de la "circunferencia de los 9 puntos" mediante relaciones cuadrangulares cíclicas entre ellos.

José Alberto García Suárez

• In this paper, the "nine points circle" theorem is proved. To achieve this, certain quadrilaterals such that three of its vertices are the middle points of the sides of the given triangle and the fourth is one of the six remaining points, are considered and proved to be cyclic.