Integer triangle common divisor. Integer triangles with a 60° angle can also be generated by with coprime integers "m", "n" with 0 < "n" < "m" (the angle of 60° is opposite to the side of length "a"). From here, all primitive solutions can be obtained by dividing "a", "b", and "c" by their greatest common divisor (e.g. an equilateral triangle solution is obtained by taking "m" = 2 and "n" = 1, but this produces "a" = "b" = "c" = 3, which is not a primitive solution). See also More precisely, If formula_109, then formula_110, otherwise formula_111. Two different pairs
Exterior angle theorem segments). Only one of these angles contains the third side of the triangle in its interior, and this angle is called an "interior angle" of the triangle. In the picture below, the angles "∠ABC", "∠BCA" and "∠CAB" are the three interior angles of the triangle. An "exterior angle" is formed by extending one of the sides of the triangle; the angle between the extended side and the other side is the exterior angle. In the picture, angle "∠ACD" is an exterior angle. The proof of Proposition 1.16 given by Euclid is often cited as one place where Euclid gives a