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折叠问题是指将平面图形折叠后变成空间图形,然后根据平面图形的数量关系研究空间图形中各元素间的数量关系问题。解决折叠问题的关键是确定折叠前后的不变量与变量。一般地,同一半平面的元素的相对位置和度量不变,特别是各点到转轴的距离不变,分别在两个半平面内的元素相对位置则发生了变化。下面举例说明。
The problem of folding refers to the folding of the graphic into the graphic of the space, and then the quantity of the elements in the graphic of the space is studied according to the number of the graphic of the graphic. The key to solving the folding problem is to determine the invariant and the variable before and after folding. Generally, the relative positions and measures of the elements in the same half-plane remain the same. In particular, the distance between each point and the axis of rotation is unchanged, and the relative positions of the elements in the two half-planes change. Here’s an example.