Triangle their internal angles, measured here in degrees. A triangle that has two angles with the same measure also has two sides with the same length, and therefore it is an isosceles triangle. It follows that in a triangle where all angles have the same measure, all three sides have the same length, and such a triangle is therefore equilateral. Triangles are assumed to be two-dimensional plane figures, unless the context provides otherwise (see Non-planar triangles, below). In rigorous treatments, a triangle is therefore called a "2-simplex" (see also Polytope). Elementary facts about triangles were presented by Euclid in books 1–4
Golden Triangle (Rocky Mountains) Golden Triangle (Rocky Mountains) The Golden Triangle is an informal designation for a region renowned as one of the premier fly fishing locations in the United States. The region is named for its approximate boundaries that form an equilateral triangle having an apex at Glacier National Park and encompassing Yellowstone National Park and the eastern portion of Idaho. Superior fly fishing also exists in the surrounding areas of the Rocky Mountains in Idaho and western Montana. Because of a large number of major rivers such as the Yellowstone, Madison, Gallatin, and the Blackfoot, many hundreds of fast, clear-running streams and