Right Angle

Pronunciation: /raɪt ˈæŋ gəl/ ?

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Angles are divided into four classes according to their measure. A right angle is an angle that measures 1/4 of a full circle[1].

Classes of Angles
Degree MeasureRadian MeasureClass Name
α<90°α<π/2 rad. Acute angle
α=90°α=π/2 rad. Right angle
90°<α<180°π/2<α<π rad. Obtuse angle
α=180°α=π rad. Straight angle
180<α<360°π<α<2π rad. Reflex angle
α=360°α=2π rad. Full angle
Table 1: Classes of angles

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  1. Keller, Samuel Smith. Mathematics for Engineering Students, Plane and Solid Geometry, pg 2. D. Van Nostrand Company, 1908. (Accessed: 2010-01-02). http://www.archive.org/stream/mathengineer00kellrich#page/2/mode/1up/search/right.
  2. Casey, John, LL.D., F.R.S.. The First Six Books of the Elements of Euclid, pg 7. Casey, John, LL.D. F.R.S.. Hodges, Figgis & Co., 1890. (Accessed: 2010-01-02). http://www.archive.org/stream/firstsixbooksofe00caseuoft#page/7/mode/1up/search/right.
  3. right angle. merriam-webster.com. Encyclopedia Britannica. (Accessed: 2009-03-12). http://www.merriam-webster.com/dictionary/right angle.

Educator Resources

  • Pythagoras Theorem and Ellipses. NASA Connect. NASA LaRC Office of Education. 2010-02-18. http://www.archive.org/details/NasaConnect-Goe-PythagorasTheoremAndEllipses.

Cite this article as:

Right Angle. 2010-01-01. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/r/rightangle.html.


Image Credits

Revision History

2010-01-01: Added "References" (McAdams, David.)
2009-12-14: Added reference to Euclid's Elements. Expanded table of angle classes. (McAdams, David.)
2008-09-16: Initial version (McAdams, David.)

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