如果三角形有一个内角为直角 ,则称这个三角形为直角三角形 ;类似地 ,四面体若有一个顶点处的三个平面角都是直角 ,则称这个四面体为直角四面体 .直角三角形与直角四面体有许多性质非常相近或相似 ,本文将给以简要归纳及论证 ,以期读者从中体验平面图形与空间图形的内在联系与 If the triangle has an interior angle that is a right angle, the triangle is called a right triangle; similarly, if the three plane angles at a vertex of a tetrahedron are all right angles, the tetrahedron is called a right-angle tetrahedron. Right-angled triangles and right-angled four-sided Many properties of the body are very similar or similar. This article will give a brief summary and demonstration, in order to allow the reader to experience the intrinsic relationship between the flat graphics and the spatial graphics.