如图一,在△ABC中,分别以AB,AC为直径在△ABC外作半圆O
1和半圆O
2,其中O
1和O
2分别为两个半圆的圆心.F是边BC的中点,点D和点E分别为两个半圆圆弧的中点.
(1)连接O
1F,O
1D,DF,O
2F,O
2E,EF,证明:△DO
1F≌△FO
2E;
(2)如图二,过点A分别作半圆O
1和半圆O
2的切线,交BD的延长线和CE的延长线于点P和点Q,连接PQ,若∠ACB=90°,DB=5,CE=3,求线段PQ的长;
(3)如图三,过点A作半圆O
2的切线,交CE的延长线于点Q,过点Q作直线FA的垂线,交BD的延长线于点P,连接PA.证明:PA是半圆O
1的切线.
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