English: Geometrical figures from Bonaventura Cavalieri's work Lo Speccio Ustorio, published 1632. They demonstrate that, for a light ray parallel to the axis of a parabola and reflected so as to pass through the focus, the sum of the incident angle and its reflection is equal to that of any other similar ray, and that if a line is extended from a point outside of a parabola to the focus, then the reflection of this line on the outside surface of the parabola is parallel to the axis.