Acute Angle
Pronunciation: /əˈkjut ˈæŋ.gəl/ Explain
Figure 1: Acute angles measure < 90° 
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 six classes according to their measure. An
acute angle is an angle that measures less than
1/4 of a full circle^{[2][3]}.

References
 McAdams, David E.. All Math Words Dictionary, acute angle. 2nd Classroom edition 201501084799968. pg 10. Life is a Story Problem LLC. January 8, 2015. Buy the book
 Keller, Samuel Smith. Mathematics for Engineering Students, Plane and Solid Geometry. pg 2. www.archive.org. D. Van Nostrand Company. 1908. Last Accessed 6/12/2018. http://www.archive.org/stream/mathengineer00kellrich#page/2/mode/1up/search/acute. Buy the book
 Casey, John, LL.D., F.R.S.. The First Six Books of the Elements of Euclid. 10th Edition. pg 4. www.archive.org. Hodges, Figgis & Co.. 1890. Last Accessed 6/12/2018. http://www.archive.org/stream/firstsixbooksofe00caseuoft#page/4/mode/1up/search/acute. Buy the book
Cite this article as:
McAdams, David E. Acute Angle. 4/11/2019. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/a/acuteangle.html.
Image Credits
Revision History
4/11/2019: Changed equations and expressions to new format. (
McAdams, David E.)
1/7/2019: Removed extraneous text about manipulative. (
McAdams, David E.)
12/21/2018: Reviewed and corrected IPA pronunication. (
McAdams, David E.)
6/12/2018: Removed broken links, changed Geogebra links to work with Geogebra 5, updated license, implemented new markup. (
McAdams, David E.)
1/1/2010: 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.)
3/3/2008: Revised other resources, added reference to radians. (
McAdams, David E.)
7/16/2007: Expanded keyword 'acute' to include 'angle'. (
McAdams, David E.)
7/12/2007: Initial version. (
McAdams, David E.)