摘要:22.选修4-1:几何证明选讲如图所示.⊙O1与⊙O2相交于A.B两点.过点A作⊙O1的切线交⊙O2于点C.过点B作两圆的割线.分别交⊙O1.⊙O2于点D.E.DE与AC相交于点P. (I)求证:.AD∥EC, (Ⅱ)若AD是⊙O2的切线.且PA=6.PC=2.BD=9.求AD的长.
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