25.在平面直角坐標(biāo)系中,A(-5,0),B(0,5),點(diǎn)C為x軸正半軸上一動(dòng)點(diǎn),過點(diǎn)A作AD⊥BC交y軸于點(diǎn)E.
(1)如圖①,若C(3,0),求點(diǎn)E的坐標(biāo);
(2)如圖②,若點(diǎn)C在x軸正半軸上運(yùn)動(dòng),且OC<5,其它條件不變,連接DO,求證:DO平分∠ADC;
(3)若點(diǎn)C在x軸正半軸上運(yùn)動(dòng),當(dāng)OC+CD=AD時(shí),求∠OBC的度數(shù).