Editing Equals sign (section)

=== Competing symbols ===
There were several other competing symbols for equality, especially outside of England around the 16th and 17th centuries, and Recorde's version made no significant influence in the European continent until 1650 or 1660. In 1559 the French monk [[Johannes Buteo]] published his ''Logistica'' using the symbol<math>\ [  </math> for equality. In 1571 [[Wilhelm Xylander]] published an edition of [[Arithmetica|Diophantus' ''Arithmetica'']] in which two parallel vertical lines {{char|{{!}}{{!}}}} were used for equality.{{Efn|He gives no clue as to the origin of the symbol. Moritz Cantor suggests that perhaps the Greek word ίσοι ("equal") was abbreviated in the manuscript used by Xylander, by the writing of only the two letters ίι.}} This version was adopted by several prominent writers, including [[Giovanni Camillo Glorioso|Giovanni Glorioso]], Cardinal [[Michelangelo Ricci]], and many French and Dutch mathematicians in the hundred years after, including [[René Descartes]] in 1621. 

A major competitor to Recorde's sign was Descartes' own symbol, introduced in his [[La Géométrie|''La Géométrie'']] (1637). In fact, Descartes himself used the sign {{char|1==}} for equality in a letter in 1640. Descartes does not give any reason for introducing his new symbol; however, [[Florian Cajori]] suggests it is because {{char|1==}} was also being used for a difference operation at the time. Due to the prominence of ''La Géométrie'', by 1675, Descartes' symbol gained favour over Recorde's in Europe, and most 17th-century writers on the continent either used Descartes' notation for equality or none at all. Around the turn of the 18th century, Recorde's notation gained favour rapidly. The dominating trend in mathematics of the time was [[History of calculus#Newton and Leibniz|differential and integral calculus]]. The fact that both Newton and [[Gottfried Wilhelm Leibniz]] used Recorde's symbol led to its general adoption.