Paper-cutting method has at least four mathematical principles. Axisymmetric If a graph is folded along a straight line, the graphs on both sides of the straight line can completely overlap each other. This graph is called an axisymmetric graph. Symmetry axis: The straight line where the crease lies is called symmetry axis. 2. The bisector of an angle leads a ray from the vertex of the angle and divides the angle into two equal angles. This ray is called the bisector of this angle. 3. Equal distribution. 4. congruent triangles.