(1)证明:∵

为直径,

,
∴

.∴

. ········································································ 3分
(2)答:

,

,

三点在以

为圆心,以

为半径的圆上. ·························· 4分
理由:由(1)知:

,∴

.
∵

,

,

,
∴

.∴

.································································· 6分
由(1)知:

.∴

.
∴

,

,

三点在以

为圆心,以

为半径的圆上. ···································· 7分解析:
略