Acute Angle
Pronunciation: /əˈkyut ˈæŋ gəl/ Explain
Figure 1: Acute angles measure < 90° 
Find the angles in the manipulative that are acute angles.
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. 
 Manipulative 1: Classes of angles. Click on the blue
point in the manipulative and drag it to change the figure. Created
with GeoGebra. Click to see gadget
Angle Class Classroom Demonstrator. 

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^{[1][2]}.

References
 Keller, Samuel Smith. Mathematics for Engineering Students, Plane and Solid Geometry. pg 2. www.archive.org. D. Van Nostrand Company. 1908. Last Accessed 8/6/2018. 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 8/6/2018. http://www.archive.org/stream/firstsixbooksofe00caseuoft#page/4/mode/1up/search/acute. Buy the book
Cite this article as:
McAdams, David E. Acute Angle. 7/10/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/a/acuteangle.html.
Image Credits
Revision History
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.)