Obtuse Angle
Pronunciation: /əbˈtus ˈæŋ gəl/ Explain
Figure 1: Obtuse angles measure > 90° and <180° 
 Manipulative 1: Classes of angles. Created
with GeoGebra. Click to see gadget full screen. 

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
 Keller, Samuel Smith. Mathematics for Engineering Students, Plane and Solid Geometry. pg 3. www.archive.org. D. Van Nostrand Company. 1908. Last Accessed 1/2/2010. 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 1/2/2010. http://www.archive.org/stream/firstsixbooksofe00caseuoft#page/7/mode/1up/search/obtuse. Buy the book
 obtuse angle. merriamwebster.com. Encyclopedia Britannica. MerriamWebster. Last Accessed 12/21/2009. http://www.merriamwebster.com/dictionary/obtuse angle.
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. 8/7/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/o/obtuseangle.html.
Image Credits
Revision History
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.)