我们将一张纸片折叠一次,纸片上就会留下一条折痕,所得折痕是一条直线.如果在纸上折出很多很多折痕直线以后,纸上能显现出一条曲线的轮廓,使得该曲线和每一条折痕直线都相切,我们就说是“折出了”这条曲线.我们把一条曲线的所有切线组成的集合,叫做该曲线的切线族.因此,我们所说的“折出一条曲线”实际上就是指折出该曲线的切线族.“折纸法”是数学教学中的一种方法, We will fold a piece of paper, the paper will leave a crease, the resulting crease is a straight line.If the paper folded a lot of crease lines, the paper can show a contour of the curve, making The curve is tangent to the straight line of each crease, and we say “folded out.” We call a collection of all the tangent lines of a curve, called the tangent of that curve. So, let’s say “Folding a curve ” is actually refers to the trimming of the curve out of the line. “Origami ” is a method in mathematics teaching,