Complex sentence: One way of formulating Thales'theorem is: if the center of a triangle's circumcircle lies on the triangle then the triangle is right, and the center of its circumcircle lies on its hypotenuse.
Split into simpler sentences: One way of formulating Thales'theorem is: if the center of a triangle's circumcircle lies on the triangle then the triangle is right, and it lies on the hypotenuse. The converse of Thales' theorem is then: the center of the circumcircle of a right triangle lies on its hypotenuse.