1.如圖1,點(diǎn)A、D在y軸正半軸上,點(diǎn)B、C分別在x軸上,CD平分∠ACB與y軸交于D點(diǎn),∠CAO=90°-∠BDO.
(1)求證:AC=BC;
(2)在(1)中點(diǎn)C的坐標(biāo)為(4,0),點(diǎn)E為AC上一點(diǎn),且∠DEA=∠DBO,如圖2,求BC+EC的長(zhǎng);
(3)在(1)中,過(guò)D作DF⊥AC于F點(diǎn),點(diǎn)H為FC上一動(dòng)點(diǎn),點(diǎn)G為OC上一動(dòng)點(diǎn),(如圖3),當(dāng)點(diǎn)H在FC上移動(dòng)、點(diǎn)G在OC上移動(dòng)時(shí),始終滿足∠GDH=∠GDO+∠FDH,試判斷FH、GH、OG這三者之間的數(shù)量關(guān)系,寫(xiě)出你的結(jié)論并加以證明.