如图,⊙中,弦与相交于点,,连接.
求证:⑴. ;⑵..
证明:
⑴.连接 ···················· 1分
∵
∴ ··················· 3分
∴ 即········ 5分
⑵.∵
∴ ················· 7分
∴····················· 8分