# Acute Triangle

Pronunciation: /əˈkjut ˈtraɪˌæŋ.gəl/ Explain

 Click on the blue points and drag them to change the figure. What can you say about the triangle when it is an acute triangle? Manipulative 1 - Acute Triangle Created with GeoGebra.

An acute triangle is a triangle where all of the angles are acute angles.[2] An acute angle is an angle with a measure of less than 90° (π/2 radians). Since all triangles that do not have a right angle are scalene triangles, all acute triangles are also acute scalene triangles.

### References

1. McAdams, David E.. All Math Words Dictionary, acute triangle. 2nd Classroom edition 20150108-4799968. pg 10. Life is a Story Problem LLC. January 8, 2015. Buy the book
2. Casey, John, LL.D., F.R.S.. The First Six Books of the Elements of Euclid. pg 8. Translated by Casey, John, LL.D. F.R.S.. www.archive.org. Hodges, Figgis & Co., . 1890. Last Accessed 6/12/2018. http://www.archive.org/stream/firstsixbooksofe00caseuoft#page/8/mode/1up/search/acute. Buy the book
3. Le Clerc, Sébastien; Nattes, John Claude; . Nattes's practical geometry, or, Introduction to perspective. pg 11. Translated by Pyne, W. H.. www.archive.org. W. Miller. 1890. Last Accessed 6/12/2018. http://www.archive.org/stream/nattesspractical00leclrich#page/11/mode/1up/search/acute. Buy the book

McAdams, David E. Acute Triangle. 4/11/2019. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/a/acutetriangle.html.

### Revision History

4/11/2019: Changed equations and expressions to new format. (McAdams, David E.)
12/21/2018: Reviewed and corrected IPA pronunication. (McAdams, David E.)
12/16/2018: Removed extraneous image. (McAdams, David E.)
6/18/2018: Changed image of acute triangle to manipulative. (McAdams, David E.)