Open
Description
Take a look at Proposition II.10: https://mathcs.clarku.edu/~djoyce/java/elements/bookII/propII10.html
Joyce's Euclid refers to angle {G} twice as {EGF} and twice as {DGB}, whatever suits the explanation better. It would be great if one could define the angle once and then use it by naming its vertex and any two points on its sides.