Euclidean geometry equal (SAS), or two angles and a side equal (ASA) (Book I, propositions 4, 8, and 26). Triangles with three equal angles (AAA) are similar, but not necessarily congruent. Also, triangles with two equal sides and an adjacent angle are not necessarily equal or congruent. The sum of the angles of a triangle is equal to a straight angle (180 degrees). This causes an equilateral triangle to have three interior angles of 60 degrees. Also, it causes every triangle to have at least two acute angles and up to one obtuse or right angle. The celebrated Pythagorean theorem (book I,
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