For a while I wanted to write more about the history behind some instruments we always use during the maths class. First on the list is the protractor.
I have put this first on the list because it is one of the basic instruments used in a geometry class. As far as I know, there is no other way to measure angles other than using a protractor. The history behind this instrument is quite interesting. The actual inventor of it is unknown, but it seems that the device was already in use during the 13th century. This is know because at that time in Europe they constructed an astronomical observing device which was equipped with a protractor. Moreover, Thomas Blundeville described a tool similar to a protractor in his 1589 Briefe Description of Universal Mappes & Cardes. As the title of the book suggests, the tool was used for preparation of maps, particularly navigational charts.
From theses, by the 17th century the mentions of protractor – like tools appeared in almost any book related to navigation (sea or land) or astronomy. Moreover, by the 18th century the tool has started to appear in different textbooks on introduction to geometry. At the end of the 18th century, in 1801, a more complex form of protractor was invented by Joseph Huddart, a US naval captain. This was designed for plotting the position of a ship on a navigational chart. The instrument is called a three-arm protractor. By the 19th century, machinists were devising a variety of specialized forms of protractors. Also, by the 20th century, protractors had become commonplace in school mathematics.
In all of this, for me it is very important to observe where the tool was used practically. I find it very useful to know that it was used first in navigation, designing maps and astronomy than in a geometry textbook.
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