Main Page | See live article | Alphabetical index In geometry, an equilateral triangle is a triangle in which all three sides have equal lengths. Equilateral triangles are also equiangular; that is, all three internal angles are also equal to each other and are each 60°. See also trigonometry. This is a stub. You can help Wikipedia by fixing it. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.