More about Areas and Volumes (1) (English subtitles available)

The concepts of arc and sector are first introduced by cutting open a cone cup. Then, students are guided to find the arc length and the area of a sector from the angle at the centre, angle of the sector, circumference and the area of a bigger circle. Through experiments, Archimedes’ discoveries about spheres and right cylinders are illustrated. Moreover, formulas for volumes of pyramids, circular cones and spheres, as well as that for surface areas of right circular cones and spheres are discussed and applied in solving problems of some public examinations.