ABSTRACT
GeoGebra is free software, that is available in and in Vietnamese. It can be used in teaching and learning in all areas of high school and it is very effective. In this chapter, we show how to use GeoGebra in teaching and learning space geometry, especially how to draw a section of a polyhedron and a conical circle, as well as, how to cut them by a plane, and related problems (calculating volume and ratio of volumes, area of cross-section, etc.). Calculating a cross-section is a difficult part of the mathematical program of geometry (Grades 11–12 of the current Vietnam High School Program), and GeoGebra proved effective in teaching and studying cross-sections.
