In junior high school, my algebra textbook was like this. My junior high school geometry textbook and later senior high school mathematics textbook have been changed. This obviously does not conform to the rules of Chinese punctuation. After all, this is China's math textbook. Only when the sentence ends with letters, numbers and other mathematical symbols should a period be used.

I saw someone reply that a period is easily confused with a percent sign or a corner sign 0. I think this is sheer nonsense. As long as we follow the rules of punctuation in Chinese grammar, it is impossible to cause confusion by using a period at the end of Chinese characters and a period at the end of letters, numbers or symbols. Moreover, there are obvious differences between a period and a percent sign, a corner sign 0 or the letter O on printed matter, which can be distinguished at a glance.