ABSTRACT
AS we showed in the last chapter, before children can coordinate measurements in such a way as to fix a point in an area or a solid, they need to evolve a system of one-one correspondences with axes perpendicular. In other words, rectangular coordination depends on the principle of one-one correspondence. The measurement of angles (portions of a plane defined by two straight lines as against four) 2 depends on the principle of one-many correspondence. This conclusion may be familiar from C.C.S., ch. XII, where we studied similarities and proportions. Here we tackle the same problem in relation to the measurement of angles and triangles.
