U konveksnom četverokutu
![ABCD](/media/m/9/c/e/9ce25711ba18d9663b73c3580de4bf5a.png)
vrijedi
![|AD| = |CD|](/media/m/2/2/3/2236f6b713746ec1957fdddb449d346f.png)
i
![\angle{DAB} = \angle{ABC} < 90^\circ](/media/m/9/9/b/99b39786c523bf41188cdd6c8c7b9aaa.png)
. Pravac kroz
![D](/media/m/7/0/0/7006c4b57335ab717f8f20960577a9ef.png)
i polovište
![\overline{BC}](/media/m/8/8/1/8818caad7d36e134c54122cbf46f1cd9.png)
siječe pravac
![AB](/media/m/5/2/9/5298bd9e7bc202ac21c423e51da3758e.png)
u točki
![E](/media/m/8/b/0/8b01e755d2253cb9a52f9e451d89ec11.png)
. Dokažite da je
![\angle{BEC} = \angle{DAC}](/media/m/6/3/0/630075fc5b6e31ac987e87880a910541.png)
.
%V0
U konveksnom četverokutu $ABCD$ vrijedi $|AD| = |CD|$ i $\angle{DAB} = \angle{ABC} < 90^\circ$. Pravac kroz $D$ i polovište $\overline{BC}$ siječe pravac $AB$ u točki $E$. Dokažite da je $\angle{BEC} = \angle{DAC}$.