Revolutionary events were changing Europe in the early 1500’s: the printing press; Asian trade; American exploration; the Reformation. The Italian peninsula was not one country but a collection of city-states with many wealthy and cosmopolitan traders. Modern algebraic notation did not exist at this time. Designating variables by letters was invented by Viète in 1591. (He used consonants for constants and vowels for variables.) Writing superscript for repeated multiplication is due to James Hume—in 1636 he used Aⅱ, Aⅲ, Aⅳ, …. Even +, –, and √ were new, having been introduced in 1486 by Johannes Widman. × was introduced by William Oughtred in 1631 and ÷ by Johann Rann in 1659. Our «equals symbol» = was introduced by Robert Recorde in 1557, in his Whetstone of Witte: And to avoide the tediouse repetition of these woordes: is equal to: I will lette as I doe often in woorke use, a paire of paralleles, or gemowe lines of one lengthe, thus: ═, because noe 2 thynges, can be moare equalle. (gemowe is an obsolete word meaning twin or, in this case, parallel.)
Joseph J Rotman (1995)
citing Robert Recorde (1557), Johann Rann (1659), William Oughtred (1631), Johannes Widman (1486), James Hume (1636), and François Viète (1591)
