 This result has been called the "pons asinorum" (the bridge of asses) or the isosceles triangle theorem.Rival explanations for this name include the theory that it is because the diagram used by Euclid in his demonstration of the result resembles a bridge, or because this is the first difficult result in Euclid, and acts to separate those who can understand Euclid's geometry from those who cannot.A well known fallacy is the false proof of the statement that "all triangles are isosceles".