Obtuse Angle
Pronunciation: /əbˈtus ˈæŋ.gəl/ Explain
Figure 1: Obtuse angles measure > 90° and <180° 
Click on the blue point and drag it to change the figure.
Can you find all 5 angle classes represented?
 Manipulative 1  Angle Classes Created with GeoGebra. 

Angles
are divided into four classes according to their measure. An
obtuse angle is an angle that measures more than
1/4 of a full circle and less than 1/2 of a full circle^{[1][2]}.
Click on the blue point in the manipulative and drag it to change the figure.

References
 McAdams, David E.. All Math Words Dictionary, obtuse angle. 2nd Classroom edition 201501084799968. pg 128. Life is a Story Problem LLC. January 8, 2015. Buy the book
 Keller, Samuel Smith. Mathematics for Engineering Students, Plane and Solid Geometry. pg 3. www.archive.org. D. Van Nostrand Company. 1908. Last Accessed 9/5/2018. http://www.archive.org/stream/mathengineer00kellrich#page/3/mode/1up/search/obtuse. Buy the book
 Casey, John, LL.D., F.R.S.. The First Six Books of the Elements of Euclid. pg 7. www.archive.org. Casey, John, LL.D. F.R.S.. Hodges, Figgis & Co.. 1890. Last Accessed 9/5/2018. http://www.archive.org/stream/firstsixbooksofe00caseuoft#page/7/mode/1up/search/obtuse. Buy the book
More Information
 McAdams, David E.. Angle. allmathwords.org. All Math Words Encyclopedia. Life is a Story Problem LLC. 3/12/2009. http://www.allmathwords.org/en/a/angle.html.
Cite this article as:
McAdams, David E. Obtuse Angle. 12/21/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/o/obtuseangle.html.
Image Credits
Revision History
12/21/2018: Reviewed and corrected IPA pronunication. (
McAdams, David E.)
9/5/2018: Removed broken links, updated license, implemented new Geogebra protocol, implemented new markup. (
McAdams, David E.)
8/7/2018: Changed vocabulary links to WORDLINK format. (
McAdams, David E.)
1/1/2010: Added "References". (
McAdams, David E.)
12/21/2009: Added reference to Euclid's Elements; Expanded table of angle classes. (
McAdams, David E.)
9/16/2008: Changed text on classes of angles to a table. Changed images 2 and 3 to one manipulative (
McAdams, David E.)
8/26/2008: Added entries to 'More Information'. (
McAdams, David E.)
7/12/2007: Initial version. (
McAdams, David E.)