Story of 'point' inside of rectangular triangle

Question

Yesterday when I was solving some basic geometry problems, I was curious ( I'm still though! ) about something:

Why / When do some people indicate the angle with its measure $= 90^\circ$ by adding a point inside it?

I like history, too, so if it's possible I want to find the story behind this notation.

Answer 1

According to Wikipedia:

In diagrams, the fact that an angle is a right angle is usually expressed by adding a small right angle that forms a square with the angle in the diagram, as seen in the diagram of a right triangle (in British English, a right-angled triangle) to the right. The symbol for a measured angle, an arc, with a dot, is used in some European countries, including German-speaking countries and Poland, as an alternative symbol for a right angle.

Note that it talks about an arc with a dot, not a square. For what it's worth, I've seen both "little square with dot" and "little square without dot" in Greece. I've never seen an "arc with dot".

I will be quite surprised if there is any particular story behind this notation. It is probably a matter of different communities using different notation for the same thing. Another example of this phenomenon concerns, e.g., the Notation for intervals.