[tex]\it Fie\ AD\cap BE =\{F\}\\ \\ Observ\breve{a}m\ c\breve{a}\ AF-bisectoare\ \c{s}i\ \^{i}n\breve{a}l\c{\it t}ime\ \^{i}n\ triunghiul\ ABE \Rightarrow \Delta ABE-isoscel,[/tex]
[tex]\it AB=BE \Rightarrow AF-mediatoarea\ laturii\ BE\\ \\ D\in AF \Rightarrow DF - mediatoarea\ laturii\ BE\Rightarrow DB=DE \Rightarrow \Delta BDE-isoscel[/tex]