Basic figures, such as triangles in Grade One, quadrangles and circles in Grade Three, mainly study their properties and relationships. For example, triangles can prove congruence, or the application of midline, quadrangles can also prove parallelograms or squares, and some basic figures will be further studied, such as translation, rotation and symmetry.
Among them, the coordinate system we study is also to develop the concept of space. The so-called space refers not only to three-dimensional graphics, but also to the ability to separate basic graphics from complex graphics, such as the combination of circles and quadrangles, and to master the concept of the nature of circles.
Pure hand tour, I hope it will help you ~