Geometric Model by A. Harry Wheeler, Supplementary Trihedral Angles


Three planes that meet at the center of a sphere form what is called a trihedral (three-sided) angle. Each plane intersects the sphere in a great circle. Segments of these three circles form a spherical triangle on the sphere. In this cut and folded tan paper model, Wheeler labels the vertices of this triangle ABC. Consider a point (not named by Wheeler – call it X) inside the bounds of the trihedral angle and drop perpendiculars to the three sides of the trihedral angle through it. Wheeler calls the points of intersection D, E, and F. The trihedral angle centered at X is the supplement of the original trihedral angle.


D. A. Low, Practical Geometry and Graphics, New York: Longmans, Green and Co., 1912, pp. 233-235.

Date Made: 1927 05 29

Maker: Wheeler, Albert Harry

Location: Currently not on view

Place Made: United States: Massachusetts, Worcester

Subject: Mathematics


See more items in: Medicine and Science: Mathematics, Trigonometry, Science & Mathematics, Spherical Trigonometry


Exhibition Location:

Credit Line: Gift of Helen M. Wheeler

Data Source: National Museum of American History

Id Number: MA.304723.195Accession Number: 304723Catalog Number: 304723.195

Object Name: Geometric Model

Physical Description: paper (overall material)tan (overall color)cut and folded (overall production method/technique)Measurements: average spatial: 7 cm x 7.3 cm x 6 cm; 2 3/4 in x 2 7/8 in x 2 3/8 in


Record Id: nmah_1066700

Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.

If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.