⑴Can you put up the Christmas tree? ____
⑵We are going to write Christmas cards to our friends. ____
⑶Santa is a merry man in red clothes. ____
⑷It's a Chinese lantern for you. ____
⑸This morning we open the gifts! ____
A. B. C. D. E.
(1)如图1,在△ABC中,BA=BC,D,E是AC边上的两点,且满足∠DBE=12∠ABC(0°<∠CBE<12∠ABC),以点B为旋转中心,将△BEC按逆时针旋转,得到△BE′A(点C与点A重合,点E到点E′处)连接DE′.求证:DE′=DE.(2)如图2,在△ABC中,BA=BC,∠ABC=90°,D,E是AC边上的两点,且满足∠DBE=12∠ABC(0°<∠CBE<∠45°).求证:DE2=AD2+EC2.