I had no idea that math symbols were so recent:
It is believed that the equals sign was invented around 1557 by Robert Recorde. Recorde was a Welsh Mathematician who first used a much larger, wider equals sign to represent two equivalent items, calling them parallel lines or “Gemowe lines” (twin lines). Recorde is reported to have found the act of having to repeatedly state that two values were equal to one another time consuming and irritating, developing a shorthand to convey the meaning of equivalency.
While Recorde’s new equals sign succinctly implied equality between two values, it wasn’t widely adopted until much later. One reason that Recorde’s symbol may have been slow to catch on was that in the 16th century Latin still heavily influenced communication, and the term “aequalis” was frequently just shortened to “Ae” or “oe” if an abbreviation was required. However, Recorde had introduced English speakers to the now-famous German symbols for subtraction and addition: “+” and “-”. This gave Recorde’s equals sign some extra influence, as when combined with + and – the equals sign could easily be used to assert mathematical equations that took much longer to write out. A vertical equals sign, rather than a horizontal equals sign, may have been used throughout the 1600s, with the now universally used horizontal equal sign becoming standardized over the course of the 1700s.
— Daniel Nelson, ScienceTrends.com
Just another thing to keep in mind if you ever travel(led) back in time to before 1600: no one could understand your math notation.
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