Spherical Trig-Easy Mathematical Chart
date: label: date made
content: 1944-1960
name: label: maker
content: Dietzgen, Eugene
notes: label: Description
content: With the outbreak of World War II, a relatively large number of Americans had occasion to learn spherical trigonometry, inspiring the invention of this small cardboard chart. Called a "Spherical TRIG-EASY," it shows on one side a right-angled triangle on the surface of a sphere with various angles and sides lettered. A disc inside has letters for possible unknown sides and angles that show at at the top and an equation for that variable in a slot on the right. The other side has equations in terms of oblique angles.
label: Description
content: The inventor, Earl H. Needham, designed several charts that were sold by Dietzgen. One was for plane trigonometry, one for trigonometry in three dimensions (e.g. on a cube), and the third, this one, for spherical triangles. Needham went on to devise charts for use in solving problems in electricity and electronics. This example of the Trig-Easy has been in the NMAH collections since at least 1984.
label: Description
content: The Trig-Easy for spherical triangles sold in 1952 for seventy-five cents. Advertisements for the Trig-Easy appeared from 1944 through at least 1960.
label: Description
content: References:
label: Description
content: Accession file 2024.0178.
label: Description
content: Glen Van Brummelen, <I>Heavenly Mathematics: The Forgotten Art of Spherical Trigonometry</I>, Princeton and Oxford: Princeton University Press, 2013, Plate 6, pp. 86-88.
label: Description
content: Eugene Dietzgen Co., <I>Price List<I>, 1952, p. 19.
label: Location
content: Currently not on view
place: label: place made
content: United States: Illinois, Chicago
setName: label: See more items in
content: Medicine and Science: Mathematics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 2024.0178.01
label: catalog number
content: 2024.0178.01
label: accession number
content: 2024.0178
objectType: label: Object Name
content: chart
physicalDescription: label: Physical Description
content: cardboard; metal (overall material)
label: Measurements
content: overall: 3 1/4 in x 3 3/4 in x 1/8 in; 8.255 cm x 9.525 cm x .3175 cm