电子课本网 第56页

第56页

信息发布者:
C
D
C
$39^{\circ}$
$25^{\circ}$
(1)证明:
$\because \triangle ABC$是等边三角形,
$\therefore \angle BAC=\angle C = 60^{\circ},$$AB = AC.$
在$\triangle ABE$和$\triangle CAD$中,
$\begin{cases}AB = CA\\\angle BAE=\angle C\\AE = CD\end{cases},$
$\therefore \triangle ABE\cong\triangle CAD(SAS).$
(2)解:
由(1),得$\triangle ABE\cong\triangle CAD,$
$\therefore \angle ABE=\angle CAD.$
$\because \angle BFD=\angle ABE+\angle BAD,$
$\therefore \angle BFD=\angle CAD+\angle BAD=\angle BAC = 60^{\circ}.$
B