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1.用直径约1.5毫米的金属丝制成三棱柱、正方体和正四面体框架(各几何体的线度3~5厘米,各接头应焊接得很光滑,没有尖棱)。 2.把三棱柱框架浸没在皂液中,取出后观察框架上皂膜的形状。发现所有的皂膜都是平的,这是皂膜相交在各条边上,有3个皂膜在中心线上相交,且交会在同一处的皂膜与皂膜间的夹角都相等(均为120°),如图a所示。
1. Triangular prism, cube and regular tetrahedron frame are made of metal wire with a diameter of about 1.5mm (the geometry of each geometry is 3 ~ 5cm, each joint should be welded with smooth, no sharp edges). 2. The prism frame immersed in the soap solution, remove the frame after observing the shape of the soap film. Found that all the soap films are flat, which is the intersection of the soap film on each side, there are three soap film in the center line intersection, and intersection in the same soap film and soap film between the same angle ( Both 120 °), as shown in Figure a.