如圖1,在平面直角坐標(biāo)系中,過點(diǎn)B(3,3)向坐標(biāo)軸作垂線,垂足分別是點(diǎn)A和點(diǎn)C,點(diǎn)D是線段OC上一點(diǎn),點(diǎn)A繞點(diǎn)D順時針旋轉(zhuǎn)90°得到點(diǎn)E.
(1)若點(diǎn)D的坐標(biāo)為(t,0),求點(diǎn)E的坐標(biāo)(用含t的式子表示);
(2)如圖2,連接AE,EC,AE交BC于點(diǎn)F,連接DF,試探究∠DEC與∠AFD的數(shù)量關(guān)系,并證明你的結(jié)論;
(3)如圖3,若點(diǎn)M是x軸負(fù)半軸上一點(diǎn),連接AM,點(diǎn)N是AM上一點(diǎn),且DM=DN=AB,ND交AO于點(diǎn)G,求△OGD的周長.