There is no fixed size. The pronunciation of this word is "appropriate", which is a unit of measurement. This means that humans or other primates will extend their arms vertically to their sides. Everyone is different. Without a fixed size, even if their height is known, it is impossible to accurately calculate the length of their arms. We must actually measure them to know.

This is the cognition of methodology, not a simple mathematical problem. In life, the use of a length is not common. If you measure your arm to make clothes, measure it with one hand, not with your arm outstretched. The most commonly used measurement method is used for the selection of athletes in certain sports, such as basketball and volleyball, which need to give full play to the advantages of height and arm length.

A person as tall as an arm;

First, it is well known that the famous basketball player Yao Ming and Yao Ming are more than two meters tall, and his wingspan length is even higher than his height. In fact, it is not surprising that everyone's wingspan exceeds his height.

Followed by Liu Xiang, although Liu Xiang is much shorter than Yao Ming, only 1.9 meters, but compared with ordinary people, it is tall and powerful enough. Liu Xiang's wingspan is also close to two meters, which laid a solid foundation for him to create a world-class running record.

Third, Liu Bei, it is said that Liu Bei's arm span reached more than two meters. The most famous example is Liu Bei reaching out and throwing his son. Of course, this is just the plot in the novel. Is there such a thing in the real world including real history? I'm afraid the history books may not know.

Fourthly, O 'Neill, a foreign friend from America, is as tall and as long as Yao Ming, which also creates favorable conditions for him to become an excellent basketball player.