Question

（6分）如圖，為外接圓的直徑，，垂足為點(diǎn)，的平分線交于點(diǎn)，連接，.
(1) 求證：；
(2) 請判斷，，三點(diǎn)是否在以為圓心，以為半徑的圓上？并說明理由.

Answer 1

（1）證明：∵為直徑，，
∴.∴. ········································································ 3分
（2）答：，，三點(diǎn)在以為圓心，以為半徑的圓上. ·························· 4分
理由：由（1）知：，∴.
∵，，，
∴.∴.································································· 6分
由（1）知：.∴.
∴，，三點(diǎn)在以為圓心，以為半徑的圓上. ···································· 7分

解析