Hands-on experience is the most effective learning. Playing mathematics through practice can be very happy! The "three-dimensional card" must comply with the "mathematical" principle in order to be able to open and close correctly. Different from plane drawing, the relationship between "length" and "angle" and its application can be understood from the assembly of three-dimensional parts. For three-dimensional cards, the level and richness of the communication will be stronger than that of flat paper. It can not only simulate the changes in the movement of objects, but also show the spatial situation.
