asses' bridge
noun
: the fifth proposition of the first book of Euclid: the angles at the base of an isoceles triangle are equal to one another
a schoolboy, stammering out his asses' bridge
Frederic Harrison
Frederic Harrison
Word History
Etymology
translation of New Latin pons asinorum; probably from the similarity of the geometrical construction demonstrating it to the trusses of a bridge and from its being considered a difficulty for poor students of geometry