Sometimes called *pons asinorum*, which, perhaps more politely, says exactly the same thing in Latin.

Germans translate the Latin into *Esels-briicke*; French use *pont aux lines*, but they all refer to the fifth proposition of the first book of Euclid:

If a triangle has two of its sides equal, the angles opposite these sides are also equal.

The proof of this simple bridge-shaped figure is so difficult for those beginning the study of geometry as to give rise to the name, whatever the native country of the student.