[tex]\it DE ||AB,\ BE-secant\breve{a} \Rightarrow \widehat{DEC} =\widehat{ABE}=80^o(\ unghiuri\ corespondente\ )\\ \\ FE ||AC,\ DE-secant\breve{a} \Rightarrow \widehat{BEF} =\widehat{ACE}=50^o(\ unghiuri\ corespondente\ )[/tex]
[tex]\it [BD - bisectoare \Rightarrow \widehat{ABD}} = \dfrac{\widehat{B}}{2}=\dfrac{80^o}{2}=40^o\\ \\ DE ||AB,\ BD-secant\breve{a} \Rightarrow \widehat{DBE} =\widehat{ABD}=40^o(\ alterne\ interne\ )[/tex]
