When using the magic ruler, the magician can display various mathematical principles by controlling the movement of the magic ruler, such as permutation and combination, multiplication principle, mathematical induction and so on.
When using the magic ruler for mathematical magic, the magician needs to master certain mathematical knowledge and apply it to the magic performance. At the same time, it is necessary to apply certain deductive ability to make the magic effect more vivid and interesting.
If you want to learn how to use the magic ruler for mathematical magic, I suggest you find relevant tutorials or courses and learn to use the magic ruler under the guidance of professional teachers.
I hope my answer is helpful to you!