Integer triangle side of the formula are integers it follows that all integer triangles must have an integer value of "16T" and "T" will be rational. By the law of cosines, every angle of an integer triangle has a rational cosine. If the angles of any triangle form an arithmetic progression then one of its angles must be 60°. For integer triangles the remaining angles must also have rational cosines and a method of generating such triangles is given below. However, apart from the trivial case of an equilateral triangle there are no integer triangles whose angles form either a geometric or
Triangle (musical instrument) form of an equilateral triangle, early instruments were often formed as non-equilateral isosceles triangles. In the early days the triangles did not have an opening and had jingling rings along the lower side. Early examples of triangles include ornamental work at the open end, often in a scroll pattern. Historically, the triangle has been manufactured from a solid iron and later steel rod and bent into a triangular shape roughly equilateral. In modern times, the scroll pattern has been abandoned and triangles are made from either steel or brass. The triangle is often the subject of jokes and one liners