EDUCATIONAL VISUAL AID PARTICULARLY FOR DEMONSTRATION IN SOLID GEOMETRY

摘要

An educational visual aid, particularly for reproducing and studying various configurations and problems in solid geometry, consisting of a ball (1), with a surface suitable for being drawn or written on, and made of transparent or translucent or some other king of material; a support (2) to hold the ball in position; and a spherical ruler, adapted to the ball surface in any position. The spherical ruler is constructed from a hoop (3), a saddle (4) perpendicular to the hoop (3), and one or more handles (5). The support (2) is a torus under the ball (1), in order to hold the ball (1) firmly in any position on the torus (2). The tracer edges of the hoop (3) and the saddle (4) lie on arcs of great circles. Between the hoop (3) and the saddle (4) of the spherical ruler, a joint (6) is inserted, perpendicular to both of them, and also adapted to the surface of the ball (1). On the inner side of the joint (6) there are two tips of contact (10, 11), appropriately spaced; on the outer side of the joint (6) there is a long-shaped, rounded supporting nose (7). The saddle (4) has a thin and solid handle plate (5) on its side preferably adjacent to the joint (6), with two rounded tips (5a, 5b) on the top of the plate (5).