Isosceles Triangle has Two Equal Angles/Also known as

Isosceles Triangle has Two Equal Angles: Also known as
This proposition is the famous pons asinorum, that is, the bridge of donkeys, supposedly for two reasons:
 * $(1): \quad$ The diagram accompanying it is supposed to look a bit like a bridge
 * $(2): \quad$ If you can't cross this bridge (that is, understand this theorem), you're supposedly a bit of a donkey.

Don't blame the students -- this is one of the more tortuous ways of proving this theorem.

Commentators have speculated that may not have known what he was doing when he wrote this.