Isosceles Triangle Theorem - Pons Asinorum

Pons Asinorum

In medieval times, when geometry was one of the four subjects of the quadrivium, this theorem acquired a reputation as an early yet difficult proposition and those who did not master its proof would be unable to go on to more advanced material. Perhaps because of this, the theorem became known as the pons asinorum or asses' bridge and is used as a metaphor for any early, difficult test.