22. 填空(请补全下列证明过程及括号内的依据)
已知:如图,
.
求证:
证明:∵
(已知),
且
(__________________________),
∴
(_______________________________),
∴
(____________________________),
∴
___________
(_________________________),
又
(已知),
∴
_________________
(等量代换),
∴
(_________________),
∴
(_________________________).