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破解难点一:探究与球有关的组合体问题与球有关的组合体问题,一种是内切,一种是外接。解题时要认真分析图形,明确切点和接点的位置,确定有关元素间的数量关系,并作出合适的截面图。如球内切于正方体,切点为正方体各个面的中心,正方体的棱长等于球的直径;球外接于正方体,正方体的顶点均在球面上,正方体的体对角线长等于球的直径。球与旋转体的组合,通常作它们的轴截面解题,球与多面体的组合,通过多面体的一条侧棱和球心、“切点”或“接点”作出截面图。
Crack a difficult one: to explore the ball and the ball with the combination of problems related to the ball, one is inside, one is external. Problem-solving should carefully analyze the graphics, clear the location of the contact point and the contact to determine the relationship between the number of elements, and make the appropriate cross-sectional view. If the ball is cut in the cube, the tangent point is the center of each face of the cube, and the edge length of the cube equals to the diameter of the ball; the ball is circumscribed to the cube and the vertices of the cube are both spherical. The cube diagonal length equals to the diameter of the ball. The combination of the ball and the rotator usually takes their axial cross-sectional solution, the combination of the ball and polyhedron, and the cross-sectional view is made by a side edge of the polygon and the center of the ball, “tangent point” or “contact point.”