A paperfolding paradise
The website of writer and paperfolding designer David Mitchell
|Summing the Angles of a Triangle|
page attempts to record what is known about the origin
and history of the method of summing the angles of a
triangle by folding alone. Please contact me if you know
any of this information is incorrect or if you have any
other information that should be added. Thank you.
As far as I know this simple demonstration by paperfolding that the angles of a triangle sum to 180 degrees was first published in the French magazine L'Illustration 2483 of 27th September 1890 and then included in the second volume of 'La Science Amusante' by Tom Tit (real name Arthur Good), which was published in Paris by Librairie Larousse in 1892.
The same demonstration also appeared:
Under the heading of 'Angulos del Triangulo' in 'Guia Practica del Trabajo Manual Educativo' by Ezequiel Solana, which was published by Editorial Magisterio Espaņol in Madrid in 1904.
In 'Scientific Amusements' by C G Knott, which was published by Thomas Nelson and Sons Ltd in London in 1918. The Preface to this book makes it clear that this book is largely a translation of some of the material from volumes 2 and 3 of 'La Science Amusante' by Tom Tit.
In 'At Home Tonight' by Herbert McKay, which was published by Oxford University Press in London, New York and Toronto in 1940, gives a way of demonstrating, by folding, that the angles of a triangle sum to 180 degrees.